Spindle Cell Oncocytoma of the Adenohypophysis

Abstract

The recently described "spindle cell oncocytoma of the adenohypophysis" is a very rare and often misdiagnosed entity. A benign biologic behavior has been suggested based on the absence of recurrences with a median follow-up of 3 years. Herein, we present 2 cases of recurrent spindle cell oncocytomas. One patient is a 71-year-old woman (case no. 1) and the other a 76-year-old man (case no. 2). Recently, both underwent transsphenoidal reexploration for recurrent "pituitary adenoma." Patient no. 1 had initial surgery 11 years ago with a recurrence after 3 years that was initially stable. Ultimately, a partial resection was performed after compression of optic pathways by the tumor, and approximately 1 year later, re-resection was carried out. Patient no. 2 had initial surgery 10 years ago with recurrence and resection after 3 years. He recently presented with a large mass that involved the pituitary fossa and base of the skull, with extension into the nasopharynx and nasal cavity. The primary and recurrent lesions of both cases showed similar architecture with interlacing fascicles of spindle cells that alternated with areas of epithelioid-like cells that exhibited eosinophilic, granular cytoplasm. Neoplastic cells were positive for vimentin, S-100 protein, and epithelial membrane antigen, and negative for glial fibrillary acidic protein, chromogranin, and pituitary hormones. Increased mitotic activity was noted in 1 lesion (case no. 2), although both cases had high Ki-67 indices (18% and 20%, respectively). The ultrastructural features of both cases were characteristic with intracytoplasmic accumulations of large mitochondria. The histopathologic features of these lesions are consistent with spindle cell oncocytoma of the adenohypophysis. In summary, we are reporting 2 cases of recurrent spindle cell oncocytoma of adenohypophysis with longer follow-up than previously published cases, suggesting the possibility of a more aggressive behavior than has been initially considered.

Spindle cell oncocytoma of the pituitary gland with follicle-like component: organotypic differentiation to support its origin from folliculo-stellate cells

“…Indeed, reported nonstandard examples of SCO tend to document features of aggressive behavior rather than any significant departure from its conventional histology [6][7][8]16].…”

Spindle Cell Oncocytoma of the Adenohypophysis With Marked Hypervascularity

“…The original description stated that 11) SCO did not contain these structures, but otherwise was demonstrated. 3,8) Interestingly, the granules were found in the primary tumor but not in recurrent tumor in one case. 8) Similarly, only a few granules were detected in our case.…”

“…3,8) Interestingly, the granules were found in the primary tumor but not in recurrent tumor in one case. 8) Similarly, only a few granules were detected in our case. These findings suggest that the detection of a few neurosecretory granules does not exclude the diagnosis of SCO.…”

“…The proliferation rate is generally low, but high MIB-1 indices (18-20%) were reported in recurrent tumors. 8) Although the MIB-1 indices of the primary tumors are not known, the proliferation rate of SCO is likely to increase according to recurrence. These findings show that initial surgery and postoperative adjuvant therapy are critical.…”

“…MIB-1 index was 3% (D: original magnification ×100). [1][2][3][4]8,9,11,12) The clinical and radiological features of SCO are nonspecific and indistinguishable from those of non-functioning macroadenoma, but its histological profile is quite different; the tumor consists of interwoven fascicles of spindle cells exhibiting abundant eosinophilic cytoplasm, rare mitosis, but no necrosis. The tumor cells show immunoreactivity for vimentin, S-100 protein, and epithelial membrane antigen (EMA), and the cytoplasm contains abundant mitochondria.…”