The clinicopathological features of pituicytoma and the differential diagnosis of sellar glioma

Abstract

Pituicytoma is rare and difficult to diagnose. This study explored the clinicopathological features, immunophenotype and differential diagnosis of pituicytoma. We compared 11 cases of pituicytoma and 26 cases of sellar glioma (16 pilocytic astrocytomas, four diffuse astrocytomas, three pilomyxoid astrocytomas, and three third ventricle chordoid gliomas). The 11 pituicytoma cases involved six men and five women (age: 33-65 years). Three of the 11 patients experienced recurrence due to a residual tumor, and one patient underwent three surgeries during a 6-month period. Imaging findings revealed tumors were in the intrasellar region (four cases), suprasellar region (four cases) and intra-suprasellar regions (three cases). The tumor diameters were 1.3-3.8 cm, and the preoperative diagnoses were pituitary adenoma, craniopharyngioma and meningioma. The tumors were solid and contained spindle or slightly chubby cells that were densely arranged with visible cleft-like or expanded sinusoid structures. The cells had vague boundaries, circular nuclei, fine chromatin, and a small nucleolus. Immunohistochemical staining of the pituicytomas revealed positive expression of thyroid transcription factor-1 (TTF-1) and S-100 protein (S-100), positive focal expression of glial GFAP;(five of 11 cases), and negative oligodendrocyte transcription factor 2 (Olig2), CD34 and neurofilament expression. The Ki67 index was 6% in one case and 1-2% in the other cases. Unlike pituicytoma, most sellar glioma cases exhibited GFAP and Olig2 expression, and negative TTF-1 expression. Third ventricle chordoid gliomas expressed TTF-1, GFAP and CD34, and were negative for Olig2. Our results indicate that pituicytoma typically involves dense arrangements of spindle or slightly chubby cells. The morphology is occasionally atypical, with ependymoma-like or meningioma-like structures, and occasionally exhibits pilomyxoid degeneration. Abundant sinusoids are characteristic of hemorrhagic tumors. The dense spindle cell arrangement is a relatively specific morphology, and staining for GFAP, TTF-1, Olig2 and CD4 may help differentiate pituicytoma from sellar glioma.

Intraoperative cytology of pituicytomas

“…We observed tissue fragments in all cases and note that the tumor cells often were closely associated with vessels. This finding mirrors what has been reported histologically; specifically that pituicytomas may show cells radiating around vessels and even have some morphologic overlap with ependymomas . Our findings are consistent with what has been previously described for pituicytomas and expands on the range of features that may be seen.…”

“…The radiologic findings of pituicytomas are nonspecific and studies have found that pituicytomas are nearly always misdiagnosed prior to surgery, likely due to their radiographic overlap with other tumors of the sellar region including pituitary adenomas, craniopharyngiomas, and meningiomas . Similar to the radiographic features, the morphologies of pituicytomas also show overlap with other tumors commonly found in the sellar/suprasellar region.…”

“…Pituicytomas have been reported to have varied histologic appearances . Similarly, we found the cytological features of pituicytomas varied across tumors and tended to fall into two categories: glial‐like and meningioma‐like with some tumors demonstrating elements of both.…”

“…Pituicytomas are nearly always radiographically misdiagnosed prior to surgery . Pituicytomas show radiographic overlap with other tumors of the sellar region including pituitary adenomas, craniopharyngiomas, and meningiomas, which contributes to the high rates of misdiagnosis . The nonspecific radiographic features and the relatively rare nature of this entity are likely reasons why “this tumor is rarely considered preoperatively.”…”

A 53‐year‐old woman with Cushing's disease and a pituitary tumor

“…Pituicytoma is supposed to derive from the neoplastic transformation of pituicytes, which are specialized glial cells of neurohypophysis . It is histologically composed of elongated bipolar spindle cells arranged in fascicles or in a storiform pattern and it has peculiar a immunohistochemical profile, with positive staining for vimentin, S100 and TTF‐1, variable (patchy to diffuse) staining for GFAP and EMA and absence of staining for cytokeratins, synaptophysin, chromogranin and pituitary hormones …”