NQ-134: (E) Germinoma

Pathology of the case: This image, when the clinical information is taken into consideration, is essentially diagnostic for a geminoma. The salient features include the presence of large cells with large nuclei, prominent nucleoli, and a small to moderate amount of cytoplasm admixed with cells with small nuclei and minimal amount of cytoplasm consistent with reactive lymphocytes (arrow). For germinoma, a good cytologic preparation is essentially diagnostic.

Germinoma is characterized by the presence of large neoplastic cells with large nuclei and prominent nucleoli and a small to moderate amount of cytoplasm admixed with reactive lymphocytes. The proportion of lymphocytes to neopalstic cells can vary greatly and granuolomatous changes, sometimes extensive, can be seen in some of these cases. The most common intracranial location of germinoma is the pineal and followed by the pituitary but the pineal takes the lion's share. 

Oncocytic pituicytomas (granular tumor, spindle cell oncocytoma, pituicytoma): Oncocytic tumors can be found arising from the posterior pituitary namely pituicytoma, granular cell tumor, and spindle cell oncocytoma. These tumors are rather uncommon but they should not be mistaken as pituitary adenoma with oncocytic changes. The 3 entities are positive for thyroid transcription factor-1 (TTF-1) and are being put under the umbrella term of oncocytic pituicytooma by some investigators. These tumors are negative for synaptophysin which separates them from oncocytic pituitary adenomas. Histologically, there is no two cell population as illustrated here and usually these tumors are not associated with significant amount of lymphocytes. These tumors are composed usually of oncocytic cells reminiscent of granular tumors arising in other parts of the body.

 

Reference:

Lymphocytic hypophysitis: However, lymphocytic hypophysitis may produce a sellar mass. Sections and cytologic smears would contain lymphocytes. However, there should not be large atypical cells like those being illustrated here. Due to the presence of some fibrosis in lymphocytic hypophysitis, the specimen usually would not smear out well. However, geminiomas tend to smear very well and getting a great cytologic smear/squash preparation from germinoma is usually easy.

Atypical teratoid/rhabdoid tumor (AT/RT): First, tis patient is too old for AT/RT. It is a tumor of infants and young children. Second, the location is wrong. AT/RT does not arise from the pituitary and presents as a sellar mass. Third, these cells have large nuclei and prominent nucleoli that can be seen in AT/RT but the nuclei in AT/RT are usually of higher nuclear grade and have more pleomorphism. Besides, there is no rhabdoid changes here in the cell. There is no classic egg shaped cells with eccentric nuclei and an inclusion like round eosinophilic staining in the cytoplasm that pushes the nuclei to the side. AT/RT are not usually accompanied by a significant amount of lymphocytes. One must note that rhaboid features in AT/RT can be so subtle to the point that it is completely lacking in a small number of AT/RT. Depending on the rhabdoid feature to diagnose AT/RT is far from fool proved.

Craniopharyngioma: This is an epithelial tumor and generally does not smear well. The epithelial cells, like other epithelial tumor cells, tend to stay together in solid sheets or clusters. If you know what a craniopharyngioima looks like, you would not even think about this diagnosis with the image being shown here.


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