Tumors

Question 1

Oncocytic pituicytomas

Answer 1

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 pituicytoma by some investigators. These tumors are negative for synaptophysin which separates them from oncocytic pituitary adenomas. These tumors are composed usually of oncocytic cells reminiscent of granular tumors arising in other parts of the body.

Question 2

Germinoma

Answer 2

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 neoplastic cells can vary greatly and granulomatous 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. Geminiomas tend to smear very well and getting a great cytologic smear/squash preparation from germinoma is usually easy.

Question 3

Dysembryoplastic neuroepithelial tumor

Answer 3

(DNET), WHO grade I. Composed of two populations of cells with the smaller ones suggestive of glial cells and the larger one suggestive of ganglionic neurons. The background is rather mucoid and microscopic mucoid cysts are common, with many of the ganglionic neurons floating in the mucoid materials. On immunohistochemistry, the ganglionic cells are positive for neurofilament proteins and have long cytoplasmic processes.
DNET is typically seen in infant and children and the most common presentation is intractable seizure. These tumors are often found in the mesial temporal lobe and tend to be cortical based. Due to its high mucoid content, they are often solitary, hyperintense well-circumscribed mass on T2-weighted images.
There are three major cell types. The oligodendroglia-like cells: They are small cells with round to oval hyperchromatic nuclei with perinuclear halo and small inconspicuous nucleoli and scanty cytoplasm. These cells are S100 positive and GFAP negative. Large ganglion cells are often found in the lesion and in the adjacent cortex. It is very common to see these ganglionic cells floating in the mucoid background. Astrocytes are present and may present as nodules resembling fibrillary astrocytoma and pilocytic astrocytomas. Specific glioneuronal element is the histological hallmark of DNETs. Specific glioneuronal elements are columns that are perpendicular to the cortical surface. They are formed by bundles of axons lined by small oligodendroglia-like cells. In between these columns are pools of mucoid material that are alcian blue positive. Large ganglion cells often float within these muoid pools. Dysplastic cortex are sometimes found in the surrounding brain.