Nonadenomatous Tumors of the Pituitary and Sella Turcica
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REVIEW ARTICLE
Nonadenomatous Tumors of the Pituitary
and Sella Turcica
Benjamin Y. Huang, MD, MPH, and Mauricio Castillo, MD, FACR
account for 5.6% to 13% of intracranial tumors in children
Abstract: While pituitary adenomas make up over 90% of all sellar
and are 10 to 20 times more common than adenomas in this
masses, there are a number of less known tumors, both malignant
population.3,6 The incidence does not vary by race or sex.4
and benign, which may arise within the sella turcica. These include
Craniopharyngiomas are derived from squamous cell
relatively common tumors such as meningiomas and craniophar-
rests in the remnant of Rathke pouch between the adenohy-
yngiomas, as well as extremely rare tumors such as pituitary
pophysis and neurohypophysis and can occur anywhere along
astrocytomas and granular cell tumors. Unfortunately, many of these
the path of the craniopharyngeal duct, from the nasopharynx
tumors lack characteristic imaging features, often making it
to the third ventricle.3,6,7 Most craniopharyngiomas have a
extremely difficult to distinguish them by imaging alone from the
suprasellar component, with only 4% to 25% being purely
more common pituitary adenoma. In this article, we review several
intrasellar.3,5,8 Two subtypes of craniopharyngioma have
nonadenomatous tumors of the sella, with a focus on their clinical
been described: the adamantinomatous type, which is
features and typical MR imaging characteristics.
predominantly a tumor of children and adolescents but
Key Words: nonadenomatous tumors, pituitary which can be seen at any age, and the papillary type, which is
seen almost exclusively in adults.9
(Top Magn Reson Imaging 2005;16:289Y299) Patients commonly present with nonendocrine symp-
toms, including headache, nausea, vomiting, and symptoms
related to compression of the optic chiasm.6 Endocrine
A lthough pituitary adenomas are the most common sellar
tumors, accounting for more than 90% of sellar masses1
and 10% to 15% of all intracranial neoplasms,2 there are other
dysfunction is less common and may be manifested in
children as growth disturbances.2,3,6 Up to 80% of children
with craniopharyngiomas have endocrine dysfunction at
tumors that arise in the sella turcica. These tumors arise from diagnosis, with 75% demonstrating growth hormone defi-
normal pituitary elements (craniopharyngiomas, pituitary ciency.10 Patients may present with hypopituitarism, hyper-
carcinomas, astrocytomas, and granular cell tumors) may be prolactinemia, or diabetes insipidus (DI).3 Treatment usually
of nonpituitary origin (meningiomas, germ cell tumors, and consists of surgical resection with or without adjuvant
lymphoma) or may be metastases. radiotherapy, based on whether gross total resection is
Many of these nonadenomatous tumors lack specific achieved. Recurrence is rare after gross total resection.
imaging characteristics and are often indistinguishable from With subtotal resection, only 47% of patients are recurrence-
adenomas by imaging alone. In many instances, a definitive free at 5 years, and only 38% are recurrence-free at 10 years.3
diagnosis is made only postoperatively, and the final On magnetic resonance imaging (MRI), craniophar-
histological diagnosis is often unexpected. Despite this, yngiomas can appear cystic, solid, or both.2,3 Cysts are seen
there are imaging findings that may be helpful in suggesting in 85% of craniopharyngiomas.11 Predominantly solid tumors
that a sellar lesion may not be an adenoma. In this article, we are 2 times more likely to be seen in adults than in children,
review several nonadenomatous sellar tumors and their whereas predominantly cystic tumors are seen in children
imaging characteristics (Table 1). roughly 50% of the time and less frequently in adults.3 Cysts
contain variable amounts of cholesterol, keratin, protein,
CRANIOPHARYNGIOMAS methemoglobin, and necrotic debris, which accounts for their
Craniopharyngiomas are common, benign neoplasms, variable appearance on MRI.12 Cystic components are
accounting for 2% to 5% of all intracranial tumors.2,3 They typically hyperintense, and less commonly isointense, to
have a bimodal age distribution with a primary peak between cerebrospinal fluid (CSF) on T1-weighted images.2 Fluid-
5 and 14 years and a second smaller peak somewhere between debris levels can be seen within the cysts. Solid components
the fifth and seventh decades. Approximately two thirds occur have variable signal intensities, and they usually enhance
in individuals younger than 20 years.4,5 Craniopharyngiomas after gadolinium administration.2,13
Calcification is typical of craniopharyngiomas and is
present in approximately two thirds of all cases; tumor
From the Department of Radiology, University of North Carolina at Chapel calcification is seen in approximately 90% of childhood
Hill, NC. craniopharyngiomas and in 50% to 70% of adult craniophar-
Reprints: M. Castillo, MD, FACR, CB no. 7510, Department of Radiology,
University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7510 yngiomas.2,7,14 Calcification is rare in papillary-type cranio-
(e-mail: Castillo@med.unc.edu). pharyngiomas.9 Computed tomography is the preferred
Copyright * 2005 by Lippincott Williams & Wilkins modality for detecting calcification.13
Top Magn Reson Imaging & Volume 16, Number 4, July 2005 289
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and are similar to symptoms observed with other sellar and
TABLE 1. Nonadenomatous Tumors of the Sella Turcica suprasellar masses.16,36 Rathke cleft cysts range in size from a
Tumors of pituitary Craniopharyngioma/Rathke cleft cyst few millimeters to very large, in excess of 4.5 cm.15Y17 When
origin Pituitary carcinoma symptomatic, cysts can be treated with partial removal or cyst
Astrocytoma (pilocytic or pituicytoma) aspiration, with a low rate of recurrence.
Granular cell tumor The primary imaging differential diagnosis is a cystic
Gangliocytoma and MGA craniopharyngioma. As with craniopharyngiomas, signal
Nonpituitary origin Meningioma intensities of the fluid in Rathke cleft cysts can be variable on
Germ cell tumors MRI, reflecting the heterogeneous composition of the fluid,
Primary CNS lymphoma which ranges from serous to mucinous.2,15Y17 The cysts are
Dermoid/epidermoid usually of higher T1 signal intensity than CSF, with the
Schwannoma majority being isointense to hyperintense to white matter,
Metastases (breast and lung cancers most common) probably reflecting the proteinaceous nature of the cyst
fluid.16,17 On T2-weighted imaging, Rathke cleft cysts demon-
strate variable signal intensity; with high protein concentra-
Solid craniopharyngiomas can be difficult to distinguish tions, there may be low signal intensity on T2-weighted images.
from adenomas. However, the apparent diffusion coefficient In contradistinction to the cysts of craniopharyngiomas, Rathke
of craniopharyngiomas is higher than that of adenomas on cleft cysts usually demonstrate thin and uniform walls, and
average49 (Fig. 1). enhancement of the walls is uncommon.2,16,17 Enhancement of
the walls of a Rathke cleft cyst may reflect inflammation or
RATHKE CLEFT CYSTS infection. Wall calcification is uncommon.2
Rathke cleft cysts, like solid craniopharyngiomas, occur One group reported the presence of T1 hyperintense, T2
along the craniopharyngeal duct and are felt to arise when hypointense, nonenhancing intracystic nodules in 10 of 13
there is incomplete obliteration of the central embryonic cleft patients with pathologically confirmed Rathke cleft cysts,
separating the anterior lobe of the pituitary from the pars corresponding to waxy, solid, intracystic masses intraopera-
intermedia. Rathke cleft cysts are differentiated from cranio- tively, probably representing concretions of desquamated
pharyngiomas by having single-layered walls of columnar or cellular debris.18 They suggest that these nodules can be
cuboidal epithelium, often containing ciliated and goblet distinguished from soft tissue nodules seen in craniopharyngio-
cells.2,15 They are common lesions and usually asymptomatic, mas by their signal intensities and lack of enhancement (Fig. 2).
reported incidentally in up to 33% of autopsy cases. Rathke
cleft cysts are 2 to 3 times more common in females than in PITUITARY CARCINOMA
males.2,16 They can be seen at any age but, when symptomatic, Pituitary carcinomas are extremely rare tumors, with
usually present between 40 and 60 years of age.2 fewer than 150 cases reported.19 They are tumors of the
Symptoms are more likely to be present when the cysts adenohypophysis that undergo discontinuous craniospinal or
are large enough to cause mass effect on adjacent structures systemic spread.19,20 In patients with pituitary carcinoma,
FIGURE 1. Craniopharyngioma. Coronal T2-weighted (A), unenhanced (B) and enhanced (C) coronal T1-weighted, and
enhanced sagittal T1-weighted MR images through the sella turcica demonstrate a multiloculated, mixed cystic, and solid
suprasellar mass. The walls of the mass enhance, and there are solid enhancing nodules (arrows) in the right anterolateral aspect of
the tumor (C). In this case, the mass is entirely suprasellar and can be easily distinguished from the normally enhancing pituitary
gland.
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FIGURE 2. Rathke cleft cyst. Unenhanced sagittal (A) and coronal (B) T1-weighted, and enhanced coronal T1-weighted (C) MR
images demonstrate a well-circumscribed, nonenhancing, hyperintense intrasellar lesion, which displaces the normally enhancing
adenohypophysis superiorly (arrows). Enhanced sagittal T1-weighted MR image in a different patient (D) shows a thin enhancing
rim; note that the contents of the cyst are hyperintense to CSF and isointense to hyperintense relative to adjacent brain parenchyma.
47% have only systemic metastases, 40% have craniospinal pituitary carcinoma cannot be made without evidence of
metastases, and 13% have both.20 Common sites of distant spread.
hematogenous spread are the liver and bone; less common There is no sex predilection, and pituitary carcinomas
reported sites include the lungs, lymph nodes, ovaries, heart, can be seen in adults of any age (mean, 44 years).19,21
pancreas, and myometrium.19,21 Craniospinal metastases Approximately 75% of pituitary carcinomas are endocrino-
usually involve the cortex, cerebellum, and cerebellopontine logically active; most are prolactin or adrenocorticotropic
angles.19 hormoneYproducing tumors.20Y22
The pathogenesis of pituitary carcinomas is not under- Clinical features of pituitary carcinoma are similar to
stood. It is likely that most develop secondary to transforma- those of invasive adenomas, with symptoms due to mass
tion of an existing pituitary adenoma rather than develop de effect on surrounding structures or to the excessive hormone
novo.21 Most pituitary carcinomas are initially diagnosed as production.19,21,22 A common clinical presentation is early
invasive macroadenomas, and there is generally a latency recurrence of tumor after resection, followed by a prolonged
period of 5 to 10 years before finding metastases.19,21 course of repeated surgeries for local recurrences, before
Histologically, there are no reliable criteria for distinguishing metastatic disease.22 Once metastases are detected, the mean
adenomas from pituitary carcinomas.20 A diagnosis of survival time is 4 years; survival varies with endocrinologic
FIGURE 3. Pituitary carcinoma. Unenhanced sagittal T1-weighted (A) and enhanced coronal T1-weighted (B) MR images
demonstrate a bilobed sellar and suprasellar mass with heterogeneous enhancement. Note the circumferential Bwaisting^ that
occurs at the level of the diaphragma sella (arrows), which is commonly seen in pituitary macroadenomas. This mass is
radiographically indistinguishable from an adenoma.
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tumor subtypes, with adrenocorticotropic hormoneYprodu- GRANULAR CELL TUMORS
cing tumors having the worst prognosis.19 Patients with only Granular cell tumors are rare and benign tumors of the
central nervous system (CNS) involvement seem to have neurohypophysis and have also been referred to as choristo-
longer survival than those with systemic metastases.19 mas, myoblastomas, and infundibulomas. They arise from
From a neuroimaging standpoint, distant spread is the granular cellYtype pituicytes,31 but structurally identical
only feature which distinguishes pituitary carcinomas from
adenomas. With regard to the primary sellar tumor,
carcinomas cannot be differentiated from invasive macro-
adenomas.19,21 Like macroadenomas, pituitary carcinomas
appear as enhancing sellar masses with suprasellar/parasellar
extension and invasion of the cavernous sinus or bone. The
metastases of pituitary carcinoma are indistinguishable from
metastases of other carcinomas21 (Figs. 3 and 4).
PITUITARY ASTROCYTOMAS
Astrocytomas arising from the pituitary gland are rare
and arise from the neurohypophysis. Astrocytomas of the
pilocytic type have been reported.23 In addition, there have
been several reports of low-grade neurohypophyseal glial
tumors, histologically distinct from pilocytic astrocytomas,
which have been referred to as pituicytomas.24Y29 Some
confusion in terminology has arisen as some authors have
used the term pituicytoma to encompass all astrocytomas
arising from the gland, whereas others consider the
pituicytoma to be a distinct entity.
The neurohypophysis contains specialized glial cells
referred to as Bpituicytes.^ Five different types of pituicytes
have been described,30 with most pituicytomas arising from
major and dark cell types.31 Pituicytomas are differentiated
from pilocytic astrocytomas by having plump, spindle-shaped
cells with a slightly fibrillar cytoplasm and by lack of Rosenthal
fibers, microcysts, and granular bodies found commonly in
pilocytic astrocytomas.24
Pituicytomas are seen from the third to ninth decades in
patients with a mean age of 40 years.24,28 There is a male
predominance.24,25,28 Pituicytomas may be entirely intrasel-
lar or suprasellar or involve both compartments. Clinical
presentation is similar to that of other sellar and suprasellar
masses, with the most common presenting complaint being
hypopituitarism, followed by visual disturbances.28 Despite
the neurohypophyseal origin of these tumors, DI is not a
common presenting symptom.25,28 Total resection is usually
curative.25
Pituicytomas and pituitary pilocytic astrocytomas are
indistinguishable from one another radiographically and, in
general, cannot be distinguished from other neurohypophy-
seal tumors. Diagnosis of pituitary astrocytoma can only be
made pathologically. For the sake of simplicity, we refer to
pituitary tumors of glial origin as pituitary astrocytomas.
MRI features of pituitary astrocytomas are nonspecific
and are those of a solid, circumscribed, enhancing sellar or
suprasellar mass, usually isointense to gray matter on T1-
weighted and hyperintense on T2-weighted sequences.24,31,29
Anterior displacement of the normally enhancing adenohy- FIGURE 4. Pituitary carcinoma metastases. Enhanced sagittal
pophysis by the tumor may suggest that it is of neurohypo- (A) and axial (B) T1-weighted MR images demonstrate
physeal origin.24 A pituitary astrocytoma containing solid and enhancing extraaxial, dural-based masses (arrows). The patient
cystic components has been reported, but the presence of had undergone resection of a prolactinoma in the past. Biopsy
cysts is an uncommon feature.24 of 1 of these lesions revealed metastatic prolactinoma.
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The imaging appearance of granular cell tumors is
nonspecific, with an enhancing sellar or suprasellar mass seen
on MRI. Eleven percent of symptomatic granular cell tumors
are intrasellar, 42% are suprasellar, and 47% involve both
compartments.32 The masses are isointense to gray matter on
both T1- and T2-weighted sequences.32,37,35 Intense enhance-
ment may be seen and reflects the high vascularity of these
tumors. Calcifications may be present. Absence of the normal
pituitary bright spot may be a clue that the tumor is of
neurohypophyseal origin, but this finding is nonspecific, as
the posterior pituitary bright spot may be absent in 10% to
20% of normal subjects38 (Fig. 5).
GANGLIOCYTOMAS
Although the pituitary gland does not contain neurons,
a small number of reports of pituitary tumors composed at
least partly of ganglion cells can be found in the literature.
These tumors are referred to as gangliocytomas. The exact
histogenesis of these tumors is debated, with some authors
suggesting that they arise from embryonal pituitary cell rests
that have features between neurons and adenohypophyseal
cells and others suggesting a common hypothalamic origin.39
The tumors are found in adults and are more common in
females.40
Although these tumors may consist exclusively of
ganglion cells, the majority (65%Y76%) of gangliocytomas
are found in association with adenomas.39Y41 Because of this,
some suggest the name, mixed gangliocytoma-adenoma
(MGA).42 Approximately 75% of patients with pituitary
gangliocytomas demonstrate pituitary hormone hypersecretion,
with oversecretion of growth hormone being the most common
manifestation, followed by Cushing disease.40,41 Interestingly,
the MGAs are more likely to be hormonally active than the pure
gangliocytomas.40 In addition to the endocrine abnormalities
seen with MGAs, visual changes and headaches can also
occur.39
On MRI, intrasellar gangliocytomas and MGAs may
not be distinguishable from pituitary macroadenomas and
FIGURE 5. Granular cell tumor. Unenhanced (A) and appear as an enhancing sellar and suprasellar mass. Some
enhanced (B) coronal T1-weighted MR images through the
have noted that the suprasellar portion of an MGA tends to be
pituitary demonstrate a well-circumscribed, enhancing nodule
arising from the pituitary stalk. more spherical than macroadenomas and that they do not
demonstrate the waist at the level of the diaphragma sella that
macroadenomas do42 (Fig. 6).
tumors have been described elsewhere in the CNS.32 They are
the most common primary tumor of the neurohypophysis33
and are seen in up to 17% of nonselected adult autopsies.34 MENINGIOMAS
The tumors are twice as common in females than in males.32 Meningiomas can originate from any dural surface,
Granular cell tumors are usually asymptomatic but, including the tuberculum sella, olfactory groove, sphenoid
when symptomatic, usually present in the fifth decade.32,35 As wing, diaphragma sella, and sella turcica.2 They account for
with other nonfunctional pituitary tumors, symptoms are approximately 20% of all intracranial neoplasms; are tumors
primarily related to size and mass effect. Tumors are usually of adults, increasing in incidence with increasing age (peak
very large when discovered.32,35 Approximately 90% of incidence, 60Y70 years); and are 2 times more common in
symptomatic patients have visual complaints, and 50% have females.2,43 Whereas 10% to 15% of meningiomas arise in
clinical or laboratory signs of hypopituitarism or hyperpro- the parasellar region, purely intrasellar meningiomas are
lactinemia.32 Headache is a common complaint. Treatment rare.2,44 The majority of intrasellar meningiomas arise from
for symptomatic granular cell tumors is surgical; post- the undersurface of the diaphragma sella, but meningiomas
operative radiation is controversial but appears to increase originating from the floor or walls of the sella have been
mean survival time and time to recurrence after surgery.32,37 reported.44
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Meningiomas are benign, slow-growing tumors. Intra- ment seen in more than 90%.7,50 The rate of enhancement is
sellar meningiomas may mimic nonfunctioning adenomas in usually rapid.51 The enhancement profile of meningiomas
their clinical presentation, with primary symptoms being may aid in distinguishing them from adenomas, as adenomas
headache, visual disturbances, visual field defects, and generally enhance less intensely and more heterogeneously
endocrinologic abnormalities (hypopituitarism or hyper- than meningiomas and demonstrate a longer time-to-peak
prolactinemia).44Y46 Cases of an intrasellar meningioma enhancement on dynamic imaging.7,50,51 The presence of
mimicking pituitary apoplexy have been reported.46,47 an enhancing dural tail is not a feature of intrasellar
Although benign, meningiomas can be locally aggressive and meningiomas.45,52
recur after incomplete resection. Encasement and, ultimately, Identification of the pituitary gland as separate from a
occlusion of an internal carotid artery can occur.2 sellar mass is probably the single most useful finding in
Preoperative diagnosis of an intrasellar meningioma is differentiating adenomas from sellar meningiomas. Visuali-
extremely useful in surgical planning and may sway surgeons zation of a CSF cleft between a tumor and the gland, although
away from the transsphenoidal approach used for most uncommon, virtually excludes the diagnosis of adenoma.7,53
adenomas in favor of a transcranial approach.47Y49 The high Another finding which may favor meningioma is hyperostosis
degree of vascularity of most meningiomas predisposes to of the floor of the sella or adjacent bony structures, seen in
excessive intraoperative bleeding during resection, which is 34% of sellar meningiomas.7,51 Prominent vessels may be
generally more easily controlled from a transcranial approach. seen in approximately 65% of sellar meningiomas.7 Macro-
Because of the vascularity of meningiomas, preoperative scopically detectable calcifications are uncommon and are
embolization of tumors is advocated by some as being helpful seen in just over 10% of sellar meningiomas7,44 (Fig. 7).
in reducing intraoperative blood loss.44 Diaphragma sella
meningiomas are typically supplied by arteries of the GERM CELL TUMORS
ophthalmic segment of the internal carotid arteries.45 Intracranial germ cell tumors are rare malignant
Purely intrasellar meningiomas can be extremely tumors, representing only 0.1% to 2% of all primary brain
difficult to distinguish from adenomas by imaging.45,48 neoplasms. They are believed to arise from totipotent germ
Intrasellar meningiomas typically appear as masses which cells that fail to migrate to the genital crest during embryonic
are hypointense to isointense to gray matter on both T1- and life. Primarily midline tumors, germ cell tumors are
T2-weighted sequences.2,7 Sellar enlargement is com- subdivided into teratomas, germinomas, embryonal cell
mon.44,45,48 Enhancement after administration of gadolinium carcinoma, choriocarcinoma, endodermal sinus (yolk sac)
is marked and homogeneous, with homogeneous enhance- tumors, and mixed germ cell tumors. Pure germinomas
FIGURE 6. Gangliocytoma. Coronal T2-weighted (A) and enhanced sagittal T1-weighted (B) MR images demonstrate a
heterogeneous, enhancing sellar and suprasellar mass. Note the spherical configuration of the mass and the absence of a Bwaist^ at
the level of the diaphragma sella.
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account for two thirds of intracranial germ cell tumors, with
nongerminomatous mixed germ cell tumors accounting for
most of the rest.54
Germ cell tumors are primarily tumors of childhood,
with a peak presentation at 10 to 12 years. Pure germinomas
occur at an older age than nongerminomatous tumors.54 The
majority of intracranial germ cell tumors are found in the
pineal or suprasellar regions. Intracranial germ cell tumors
occur twice as often in males than females, but this male
predominance is limited to tumors arising in the pineal
region. Suprasellar germ cell tumors occur slightly more
frequently in females.55,56 Pure germinomas are radio-
sensitive and carry a favorable prognosis. More than 90%
of germinomas can be treated effectively with radiation.
Prognosis for patients with nongerminomatous tumors is less
favorable, with only 40% to 60% demonstrating disease
control with radiation therapy alone.55
Primarily intrasellar germinomas are rare and have a
female predominance.57 Most suprasellar germinomas origi-
nate either in the floor of the third ventricle or in the
infundibulum. It is felt that intrasellar germinomas represent
FIGURE 7. Meningioma. Enhanced coronal T1-weighted MR
infundibular tumors with primarily intrasellar growth.57 image demonstrates a sellar and suprasellar mass with marked
Patients most commonly present with endocrine abnormal- enhancement.
ities, with DI being the most common symptom to prompt
patients to seek medical attention.57,58 Development of DI is
related to invasion or compression of the posterior lobe or Larger sellar/suprasellar germ cell tumors have a
infundibulum and may persist for years before a diagnosis is nonspecific imaging appearance and usually cannot be
made. Other manifestations include hypopituitarism in distinguished from other tumors. The MR findings are those
children and adolescents and hypogonadism in adults.57 of an enhancing solid sellar mass, with or without suprasellar
Hyperprolactinemia and precocious puberty have been extension. Cysts and calcifications may be seen.61 Differential
observed.57,59 Large tumors and primarily suprasellar tumors enhancement of the tumor and the enhancing displaced
may present with visual changes or oculomotor palsies. 58,59 anterior lobe may aid in distinguishing these tumors from
Serum tumor markers can be extremely useful in adenomas.60,62 Although rare, cavernous sinus invasion has
establishing the diagnosis of a germ cell tumor. Production of been reported to occur with larger tumors58 (Fig. 8).
either >-fetoprotein (AFP) or A-human chorionic gonado-
tropin (BHCG) can be seen in a number of subtypes of germ LYMPHOMA
cell tumors. Tumors with a yolk sac component secrete AFP. CNS lymphoma may be primary or metastatic. Less
Choriocarcinomas produce high levels of BHCG. Patients than 1% of metastases to the pituitary are secondary to
with pure germinomas can secrete BHCG into the CSF at low lymphoma.63 Primary CNS lymphoma refers to disease
levels, and this is considered an early indication of CSF limited to the craniospinal axis, without systemic disease.64
dissemination. Because other intracranial tumors do not It represents up to 2% of all primary CNS malignancies and is
produce AFP or BHCG, the presence of these markers in CSF practically always of the non-Hodgkin type, with the majority
or serum in the setting of an intracranial tumor is essentially being B-cell lymphoma.65 The incidence of CNS lymphoma
diagnostic of a germ cell tumor.54,55 has more than tripled in the United States since the early
Because intracranial germ cell tumors have a predilec- 1980s,66 due to the increase in number of immunocompro-
tion to disseminate via CSF, MRI of the entire craniospinal mised individuals. In patients with AIDS, primary CNS
axis and lumbar puncture for cytology are mandatory.54 MRI lymphoma makes up 3% of intracranial neoplasms. Interest-
cannot reliably differentiate the different types of germ cell ingly, the incidence of primary CNS lymphoma has also been
tumors. The earliest finding in cases of neurohypophyseal increasing in the nonimmunocompromised population.64,66,67
germ cell tumors is probably absence of the normal posterior Primary CNS lymphoma is considered by the US Centers for
lobe bright spot on T1-weighted images. This can be followed Disease Control to be an AIDS-defining illness in those
by swelling of the stalk and subsequent mass formation, infected with HIV. The mean age at presentation is
which may displace the enhancing pituitary gland anteriorly. significantly lower for immunocompromised patients (mean
Loss of the normal pituitary bright spot and thickening of the age, 30Y40 years) versus immunocompetent patients (mean
stalk are also seen with idiopathic DI, granulomatous age, 60Y70 years); males are more frequently affected. There
processes, and lymphocytic hypophysitis. Because of this, does not appear to be a sex predilection in the immunocom-
some have proposed serial MRI and endocrinologic evalua- petent population.65
tions in patients presenting with DI and loss of the posterior Primary lymphoma arising in the sella is exceedingly
bright spot without a definite mass.60 rare, with only a handful of cases reported.68Y74 Patients range
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in age from 44 to 86 years. Presenting symptoms are not normal immune systems usually appears as a solitary mass
specific and include headaches, hypopituitarism, visual field with intermediate to low signal intensity relative to gray
deficits, and oculomotor palsies. matter on both T1- and T2-weighted sequences; enhancement
The imaging appearances of primary CNS lymphoma with gadolinium is seen in nearly all cases and is homogenous
tend to differ based on whether patients have normal or in approximately three quarters of cases.75,65 The relative
suppressed immunity. CNS lymphoma in patients with lack of T2 prolongation in CNS lymphoma is generally
attributed to dense cellularity and to a high nuclear-
cytoplasmic ratio and may be helpful in distinguishing
lymphoma from other CNS tumors; unfortunately, this
finding is relatively insensitive, as it is seen in just over
50% of cases.65 Calcification and hemorrhage in CNS
lymphoma are rare.75
In immunocompromised patients, lesions of CNS
lymphoma are likely to be multiple and to demonstrate
necrosis.65 In the setting of necrosis, the center of the lesion is
T2 hyperintense, whereas the periphery remains of inter-
mediate to low signal.75 Contrast enhancement is hetero-
geneous in this population, and rim enhancement is more
common.65,75
MRI characteristics of sellar lymphomas are largely
nonspecific, with most cases appearing as homogeneously or
heterogeneously enhancing sellar masses.70,72Y74 Isointensity
to hypointensity of masses relative to gray matter on T2-
weighted imaging has been reported in sellar lymphoma70,74
and may be helpful in distinguishing it from pituitary
adenoma.
METASTASES
Metastases to the pituitary gland and sella are
uncommon. In surgical series examining patients undergoing
transsphenoidal surgery for sellar or parasellar tumors,
metastases are found in less than 1% of cases.63 In autopsy
series, evidence of metastases to the pituitary is seen in
approximately 5% of patients with known malignancy. In
approximately two thirds of these cases, the pituitary is
macroscopically normal.75 The most common primary
malignancies to metastasize to the pituitary gland are breast
and lung cancers which together account for more than 60%
of all pituitary metastases.63,76 In 1 review, metastases to the
pituitary were found in 17.6% of autopsies of patients with
breast cancer.63 Although breast and lung cancers are the
most common primaries to metastasize to the pituitary,
metastases from tumors of nearly every tissue type have been
reported.63
Metastases can reach the sella turcica via hematogen-
ous spread, spread from a hypothalamic or hypophyseal
metastasis through portal vessels, direct extension from skull
base tumors, or meningeal spread.63 Hematogenous metas-
tases to the pituitary have a predilection to involve the
posterior lobe. In 1 review of 201 cases of pituitary
metastases, the posterior lobe alone was involved in 50.8%
of cases, both lobes were involved in approximately 33.8% of
cases, and the anterior lobe was involved in 15.4% of cases.77
The relative infrequency of metastases exclusive to the
anterior lobe has been attributed to its lack of a direct arterial
FIGURE 8. Germ cell tumor. Unenhanced (A) and enhanced blood supply.2,63 It is hypothesized that the first capillary bed
(B) sagittal T1-weighted images demonstrate a bilobed sellar of the portal system may trap metastases before they can
and suprasellar mass with heterogeneous enhancement. travel to the anterior lobe.2 Therefore, metastatic involvement
Cysts are present within the mass. of the adenohypophysis is more often due to contiguous
296 * 2005 Lippincott Williams & Wilkins
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field deficits, anterior pituitary insufficiency, oculomotor
palsies, and headache.63,76
Imaging features of pituitary metastases are variable,
and in the absence of coexistent brain metastases, differentia-
tion from an adenoma is difficult. On MRI, pituitary
metastases appear as sellar or suprasellar masses which
often are isointense or hypointense to gray matter on T1-
weighted images and are usually of increased T2 signal. They
enhance after gadolinium administration. Enhancement may
be homogeneous or heterogeneous, and rim enhancement can
also be seen.2,63 Like macroadenomas, metastases can appear
as dumbbell-shaped intrasellar and suprasellar tumors.
Invasion of the cavernous sinus and underlying sphenoid
sinus may be seen.63 Loss of the normal posterior bright spot
FIGURE 9. Metastasis. Coronal T2-weighted (A) and
unenhanced (B) and enhanced (C) coronal T1-weighted
images through the sella demonstrate a predominantly rim
enhancing sellar mass with suprasellar extension. Central areas
of T1 hyperintensity in B and T2 hypointensity in A probably
reflect hemorrhage. The mass displaces the optic chiasm
superiorly. This was a metastasis from breast cancer.
spread from the posterior lobe than to direct hematogenous FIGURE 10. Melanoma metastasis. Unenhanced sagittal
spread.78 T1-weighted (A) and coronal T2-weighted (B) MR images
Probably because of the predilection for metastases to demonstrate a sellar mass which is markedly hyperintense on
involve the posterior lobe, the most common symptom the T1-weighted image and hypointense on the T2-weighted
observed in patients with pituitary metastases is DI, which image relative to adjacent brain parenchyma. The signal
occurs in 45% of cases.63 Other signs/symptoms include visual characteristics presumably are due to the presence of melanin.
* 2005 Lippincott Williams & Wilkins 297
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has been reported.79 Rapid growth of tumor, infundibular 21. Scheithauer BW, Kurtkaya-Yapicier O, Kovacs KT, et al. Pituitary
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