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Considered a neoplasm of pituicytes, pituicytoma is a rare and distinct type of glioma that arises in the suprasellar space and within the sella turcica. Only 12 previously reported cases of pituicytoma are documented in the literature. We report an intrasellar pituicytoma in a 66-year-old man presenting with symptoms and radiologic appearance indistinguishable from a nonfunctional pituitary adenoma. The patient also had a medical history significant for parathyroid adenomas and follicular carcinoma of the thyroid. The intrasellar tumor had morphologic features of a pituicytoma, with interlacing fascicles and a storiform pattern much like a benign fibrous histiocytoma. Immunoreactivity for S100 was strong, but the tumor lacked intercellular collagen type IV. The differential diagnosis of a low-grade spindle cell lesion of the sellar space is discussed, and the literature is reviewed. A summary of the clinical and pathologic features of this case, as well as the 12 previously reported cases, is presented.

Cholesterol emboli are known to imitate a variety of disease processes, thereby leading to delayed diagnosis. We describe a patient with a localized polypoid mass of the colon without endoscopic evidence of generalized ischemic colitis. Histologic evaluation revealed this polyp to be the result of localized ischemia with identifiable submucosal atheroemboli. Localized polyp formation appears to be a rare manifestation of atheroemboli; consequently, focal ischemia, caused by atheroemboli, should be added to the differential diagnosis of polyps of the colon.

Surgical biopsy specimens of multiple sclerosis plaques have been only infrequently reported, and the scanty descriptions of these specimens have generally emphasized the inflammatory nature of the lesion. We present surgical specimens from four patients with multiple sclerosis on whom biopsies were performed because of clinical features mimicking brain tumor. Both general pathologists and neuropathologists involved with these cases experienced difficulty in arriving at the correct diagnosis. In all four cases, the lesions were remarkably uniform in microscopic appearance, consisting of monotonous sheets of gemistocytic astroglia interspersed by numerous foamy macrophages. In sections stained with hematoxylin-eosin, the most helpful diagnostic features were the even distribution of the foamy macrophages and the absence of associated necrosis. In each case, the diagnosis was confirmed with special stains that disclosed total destruction of myelin sheaths with relative preservation of axons. Significant inflammatory infiltration was present in only one of five biopsy specimens.

We report a case of extramammary Paget's disease (EMPD) arising in the knee region in association with an underlying sweat gland carcinoma. Inguinal lymph node metastases were present initially. Paget's cells, intradermal tumor cells, and metastatic tumor cells showed similar reactions to a variety of histochemical stains and positive results with immunohistochemical staining using carcinoembryonic antigen (CEA). Control sections in cases of Bowen's disease and superficial, spreading malignant melanoma showed a negative staining reaction with CEA, providing further evidence that this technique is useful in distinguishing Paget's disease (PD) from histologically similar conditions. We provide a summary of previous cases of EMPD arising in unusual locations and a brief consideration of possible mechanisms of the origin of PD.