59‐YEAR‐OLD MALE WITH PANHYPOPITUTISM

CLINICAL HISTORY

A 59‐year‐old male teacher developed symptoms of panhypopituitarism. Magnetic resonance imaging revealed a solid homogeneously enhancing mass in the sella measuring 1.8 cm extending into the suprasellar cistern, causing mild compression of the optic chiasm (Figure 1). Neurological exam was normal other than a small bitemporal visual field defect. The lesion was suspected to be a pituitary adenoma, and a transsphenoidal resection was performed. Intraoperatively, the lesion was noted to be posterior to the anterior pituitary gland. Postoperatively, a small amount of residual tumor was present that has been stable on follow‐up neuroimaging. No adjuvant therapy was given.

Figure 1.

MICROSCOPIC DESCRIPTION

The resected specimen consisted of a fascicular and storiform arrangement of elongated cells with abundant eosinophilic cytoplasm lacking granularity (Figure 2). The nuclei were spindled and monotonous with fine chromatin and small nucleoli (Figure 3). No mitotic figures were seen. Immunohistochemical studies for chromogranin and pituitary hormones were negative. The lesional cells expressed glial fibrillary acidic protein (GFAP) (Figure 4), protein gene product (PGP) 9.5 (focal) and S100 (weak). Electron microscopy showed lesional cells bearing abundant intermediate filaments and rare neurosecretory granules (5, 6).

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

DIAGNOSIS AND DISCUSSION

Diagnosis

Pituicytoma.

Discussion

Pituicytomas are rare primary tumors of the neurohypophysis 3, 4, 5. The putative cell of origin is the pituicyte, which is a glial cell normally residing in the posterior pituitary and pituitary stalk, the function of which is thought to be the regulation of hormone secretion from the neurohypophysis. Alternatively, some authors have proposed the folliculostellate cell, an S100‐expressing cell of the anterior pituitary, as the cell of origin. The natural history of the pituicytoma is not well understood because of their rarity, although the largest case series in the recent years suggests that complete resection may be curative. However, there is a chance of recurrence following subtotal resection with the role of adjuvant therapies being uncertain at this time (2).

The histology of the current case is typical of a pituicytoma: fascicles of elongated, non‐granular cells with a rich capillary network and little evidence of proliferation (1). Their immunohistochemical profile is that of S100 and GFAP expression, with variable expression of neuron‐specific enolase and PGP9.5. The differential diagnosis includes granular cell tumor, however, the cytoplasm of the former lacks granularity or periodic acid‐Schiff positivity. An astrocytoma (especially of a pilocytic nature) may be considered, but the pituicytoma lacks a biphasic growth pattern, Rosenthal fibers or eosinophilic granular bodies. Meningioma is also a consideration, but one usually resolved by the absence of epithelial membrane antigen expression and lack of meningothelial ultrastructural features. Finally, schwannoma may enter the differential diagnosis, but is ruled out by the GFAP expression and ultrastructural features.

ABSTRACT

A 59 year old male teacher developed symptoms of pan‐hypopituitarism. MRI revealed a solid homogeneously enhancing mass in the sella measuring 1.8 cm extending into the suprasellar cistern causing mild compression of the optic chiasm. The resected specimen consisted of a fascicular and storiform arrangement of elongated cells with abundant eosinophilic cytoplasm lacking granularity. No mitotic figures were seen. Immunohistochemical studies for chromogranin and pituitary hormones were negative. The lesional cells expressed GFAP, PGP9.5, and S100. Electron microscopy showed lesional cells bearing abundant intermediate filaments and rare neurosecretory granules. The final diagnosis was pituicytoma. Pituicytomas are rare primary tumors of the neurohypophysis. The putative cell of origin is the pituicyte, which is a glial cell normally residing in the posterior pituitary and pituitary stalk, the function of which is thought to be the regulation of hormone secretion from the neurohypophysis. The natural history of the pituicytoma is not well understood due to their rarity, although the largest case series in recent years suggests that complete resection may be curative. However, there is a chance of recurrence following sub‐total resection with the role of adjuvant therapies being uncertain at this time.