Case Study 45

Julia Kofler, M.D.

Question 1 Clinical history:

41 year old male with a 2 year history of progressive hypopituitarism, headache and bitemporal hemianopsia.

Describe the lesion on the following CT scan (no MRI images available due to pacemaker).

Question 1 CT with contrast

Answer

Diffusely contrast-enhancing suprasellar mass

Question 2

What is your differential diagnosis based on the radiologic appearance and location of the lesion?

Answer

  Pituitary adenoma Craniopharyngioma      Pituicytoma Granular cell tumor Meningioma Pilocytic astrocytoma Germ cell tumor

Question 3

An endoscopic endonasal resection was performed. An intraoperative consultation was requested. What is your interpretation of the following frozen section and smear preparation?

According to the surgeon, the mass extended around the pituitary stalk and appeared highly vascular Click

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to view frozen section slide.

Click

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to view smear preparation.

Answer

 Low-grade spindle cell tumor  A pituicytoma was favored over other spindle cell neoplasms

Question 4

Describe the findings on the permanent section.

Click

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to view slide.

Answer

      Moderately cellular neoplasm Comprised of mildly pleomorphic spindle cells with variably distinct cell borders, irregular vesicular nuclei and light eosinophilic cytoplasm with a fibrillar quality Cells are arranged in groups and haphazardly interwoven fascicles The fascicles are separated by very thin, compressed vascular channels No mitoses are seen No Rosenthal fibers, eosinophilic granular bodies, Herring bodies or oncocytic change is seen

Question 5

What is your differential diagnosis and which stains may be useful to support your diagnosis?

Answer

 Pituicytoma, normal infundibulum, pilocytic astrocytoma, spindle cell oncocytoma, granular cell tumor  PAS, S100, GFAP, Neurofilament, EMA, Synaptophysin

Question 6

What is your interpretation of the following stains?

Click

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to view PAS slide Click

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to view S100 slide Click

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to view GFAP slide Click

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to view neurofilament slide

Answer

  PAS is negative in tumor cells S100 shows strong nuclear and cytoplasmic reactivity  GFAP is negative in the tumor cells (may be variably positive in pituicytomas)  Neurofilament highlights rare infundibular axons at the margin of the specimen  The tumor was also positive for vimentin and negative for synaptophysin and EMA

Question 7

Name a few features that distinguish pituicytoma from normal infundibulum.

Answer

 Normal infundibular tissue is usually less cellular than a pituicytoma (but cellularity may overlap)  Normal tissue is looser in texture and contains axons and perivascular fibrillar zones  Normal tissue contains Herring bodies (PAS positive focal axonal swellings)  Normal tissue is diffusely positive for synaptophysin and neurofilament; pituicytomas are negative

Question 8

Name a few features that distinguish pituicytoma from pilocytic astrocytoma.

Answer

 Pilocytic astrocytomas commonly occur in children, whereas pituicytomas are usually seen in adults  Pituicytomas lack Rosenthal fibers and eosinophilic granular bodies that are commonly seen in pilocytic astrocytomas  Pilocytic astrocytomas usually exhibit a biphasic growth pattern and more variability (compact, piloid, microcystic patterns)

Question 9

Name a few features that distinguish pituicytoma from spindle cell oncocytoma.

Answer

 Spindle cell oncocytomas are composed of interlacing fascicles of spindled to epithelioid cells with eosinophilic to oncocytic cytoplasm  Ultrastructurally, numerous mitochondria are seen  Spindle cell oncocytomas are usually positive for vimentin, EMA, S100 and galectin-3  They are negative for pituitary hormones, GFAP and synaptophysin

Question 10

What is your final diagnosis?

Answer

Pituicytoma

Question 11

Name a transcription factor that has recently been shown to be expressed in human fetal and adult pituicytes as well as in a variety of sellar masses (pituicytoma, granular cell tumor, spindle cell oncocytoma)?

Answer

Thyroid transcription factor 1, which was also positive in our pituicytoma (see image below) Reference: Lee EB et al. J Neuropath Exp Neurol 2009;68:482