40‐YEAR OLD FEMALE WITH A SELLAR MASS

Clinical History and Imaging Studies

A 40‐year‐old female presented with new‐onset seizures 4 months ago and with a menstrual disorder for the past 2 months. She was admitted to our hospital for evaluation. Physical examination was non‐specific. MRI of the brain revealed a well‐delineated homogeneously contrast‐enhancing mass in the posterior lobe of the hypophysis. No abnormal signal was found in brain parenchyma. Serum levels for LH, FSH and prolactin were within normal limits as were progesterone and estrogen. MRI demonstrated a sellar mass measuring about 3.6 × 3.5 mm in size. The lesion was generally isointense to gray matter on T1‐weighted images (Figure 1a) and isointense to slightly hyperintense on T2‐weighted images (Figure 1b). The patient was diagnosed with a presumed pituitary microadenoma and epilepsy, and an endoscopic transphenoidal resection was performed.

Figure 1.

‪

Gross and Microscopic Pathology

On endoscopic view, a gray‐white, well circumscribed intrasellar mass was found. The tumor appeared soft and did not adhere to the optic chiasm. Microscopically, the tumor consisted of a sheets of spindled cells arranged in interlacing fascicles and bundles (Figures 2 and 3). The tumor had fibrillar cytoplasm and slightly pleomorphic nuclei that were oval and elongated with small nucleoli. There were no Rosenthal fibers, granular eosinophilic bodies, or Herring bodies. Mitoses were absent. MIB‐1 proliferation index was very low (<1%, Figure 4a). There was no endothelial proliferation or necrosis. The tumor cells exhibited strong immunoreactivity for S100 protein (Figure 4b), patchy staining for glial fibrillary acidic protein (GFAP, Figure 4c) and Epithelial Membrane Antigen (EMA, Figure 4d. The tumor was negative for Progesterone Receptor and Neu‐N.

Figure 2.

‫

Figure 3.

‬

Figure 4.

‭

What is the diagnosis?

Diagnosis

Pituicytoma.

Discussion

Tumors of the adenohypophysis are the principal tumors of the sellar region, and also are among the most frequent primary intracranial neoplasms seen in clinical practice. They represent approximately 10–15% of all operated intracranial tumors. The overwhelming majority of neoplastic lesions arising in the adenohypophysis are adenomas. Diseases of the hypothalamus comprise tumors, inflammatory and infectious diseases, and genetic disorders. Tumors found in the hypothalamus and neurohypophysis include granular cell tumor, craniopharyngioma, germinoma, teratoma, meningioma, glioma. Inflammatory diseases include sarcoidosis, histiocytosis, etc. Infectious diseases such as meningitis (tuberculous, bacterial, viral or fungal) are also found in the hypothalamus and neurohypophysis. A rare and little‐studied neoplasm occurring in this location, the pituicytoma or infundibuloma, is one of the few primary tumors of the neurohypophysis. The term pituicytoma was historically also used for other tumors in the sellar and suprasellar region (granular cell tumors, pilocytic astrocytomas), but this term is now reserved for low‐grade glial neoplasms that originate in the neurohypophysis or infundibulum and that are distinct from pilocytic astrocytomas. To date, only a few microscopically proven cases have been reported in the literature 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Pituicytoma was believed pathologically to arise from the “pituicyte”, a specialized glial cell of the neurohypophysis 1. Microscopically, pituicytomas have a solid, compact architecture and consisting almost entirely of elongate, bipolar spindle cells arranged in interlacing fascicles or in a storiform pattern. Tumors can show dense adherence to adjacent structures. Individual tumor cells contain abundant eosinophilic cytoplasm and cell shapes range from short and plump to elongate and angulated. There is no significant cytoplasmic granularity or vacuolization. Nuclei are of moderate size, oval‐to‐elongate, with little or no atypia. Mitotic figures are rare. Reticulin stain shows a perivascular distribution, intercellular reticulin being sparse. Important for the differential diagnosis with pilocytic astrocytoma and normal neurohypophysis, pituicytomas show no Rosenthal fibers or eosinophilic granular bodies. In this case, histological examination showed the characteristic of pituicytoma. Immunohistochemical staining of the tumors demonstrated diffuse, strong positive staining for S‐100. The tumor cells were immunonegative for synaptophysin, patchy positive staining for glial fibrillary acidic protein 1, 3, and EMA 3. There was no immunostaining of tumor cells by Neu‐n and Progesterone receptor. In summary, pituicytoma should be included as a rare differential diagnosis in patients with well‐enhanced homo geneous lesions in the sellar.

Abstract

Pituicytoma is a rare, low‐grade neoplasm that originates in the neurohypophysis of the pituitary gland. We report the clinicopathologic features of a pituicytoma arising in a 40‐year‐old female who presented with menstrual disorder for 2 months, clinically suggestive of a pituitary microadenoma. The tumor was marked by a proliferation of elongated cells arranged in bundles and interlacing fascicles. The tumor demonstrated positive staining with S‐100 protein and patchy staining for glial fibrillary acid protein and Epithelial Membrane Antigen. The tumor did not stain with antibodies to Progesterone receptor and Neu‐n. An MIB‐1 labeling was lower than 1%. The tumor was subtotally resected and didn't recur after the initial surgery.