Spindle cell oncocytoma of the adenohypophysis is a recently described, spindle and granular cell, S-100 protein-positive, GFAP-negative, neuroendocrine marker-negative, mitochondria-rich neoplasm of uncertain histogenesis that can clinically and radiologically mimic pituitary adenoma. We present two cases of this entity to extend understanding of this unusual tumor. The first case was a 26-year-old man who presented with a 6-month history of progressive headache, blurred vision in the right eye, nausea, vomiting and impotence. Magnetic resonance imaging (MRI) revealed a rounded, 1.5to 2-cm homogeneously enhancing mass in the pituitary region, which involved the right cavernous sinus, impinged on the temporal lobe and expanded the sella. At transsphenoidal exploration, the mass was firm and difficult to dissect. Following this procedure, visual acuity in the right eye worsened and he underwent a right pterional craniotomy with subtotal resection of the tumor, with residual tumor remaining around the carotid artery. The patient received proton beam radiotherapy to a total dose of 54 Gy over a period of 2 months, during which his vision improved significantly. He has been followed with serial MRI, visual and endocrine examinations for 7 years and remains stable, without tumor regrowth. The second case was a 55-year-old woman who presented with headache and progressive visual deterioration over 6 months, worse in the left than right eye, as well as a 10-day history of vomiting. MRI showed a 6.5·3.3·4 cm sellar and parasellar mass. A transsphenoidal gross total excision was performed. The tumor was highly vascular with destruction of the sellar floor. Six months following surgery, her visual acuity is improved and she has no evidence of recurrence. The two tumors were histologically similar. Case 1 was predominantly composed of spindle cells in a fascicular arrangement (Fig. 1A) with foci of oncocytic appearance (Fig. 1B). Case 2, although also largely spindled in appearance, had more polygonal cells that formed ill-defined lobules (Fig. 1C, D). The cells in both cases had abundant, granular eosinophilic cytoplasm and nuclei that were only mildly pleomorphic. Neither mitotic activity nor necrosis was noted. On immunohistochemical evaluation, the tumor cells were positive for both S-100 protein (Fig. 1E) and epithelial membrane antigen, but did not stain for GFAP, pituitary hormones (prolactin, growth hormone, TSH, ACTH, FSH, LH), chromogranin or synaptophysin . The MIB1 index was approximately 1% in case 1 and 8% in case 2. Electron microscopy was performed on case 2, and showed the tumor cells to be rich in mitochondria with scattered rare secretory granules, but without complex membrane interdigitations or desmosomes (Fig. 1F). Only seven spindle cell oncocytomas of the adenohypophysis have been reported to date [5, 10]. These seven patients were older adults (ranging from 53 to 76 years), five presenting with pan-hypopituitarism and four complaining of visual defects. All five of the lesions initially reported [10] were considered benign since they lacked invasion and showed low proliferative activity. The mean follow-up period for this first series was 3 years, with the longest follow-up 68 months; none of the five tumors had recurred or metastasized. Kloub et al. [5], however, reported two cases of spindle cell oncocytoma of the adenohypophysis that recurred, raising a question about the predicted behavior of these lesions. Although the morphological features of the two primary tumors were not predictive of aggressive behavior, the recurrent tumors had high Ki-67 labeling indices (18–20%) in addition to one recurrent case with mitotic activity and necrosis. These higher proliferation S. Dahiya AE E. T. Hedley-Whyte AE D. N. Louis (&) Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA E-mail: dlouis@partners.org
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Open Access
Mar 9, 2021
Dong Ja Kim + 4
