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Two examples of large, multiloculated, cystic tumors that arose within the pelvis in men of 28 and 37 years of age are described. The tumors were composed of glands and cysts lined by prostatic-type epithelium lying in a hypocellular fibrous stroma. The prostatic nature of the lesions was confirmed by immunohistochemical staining of the epithelium for prostate-specific antigen and prostatic acid phosphatase. Two apparently similar lesions were found in the literature; one tumor was attached to the prostate by a pedicle, and the other arose in the retrovesical space. These tumors, for which we propose the designation "giant multilocular prostatic cystadenoma," appear to be benign, although they may recur if incompletely excised. They may pose considerable diagnostic difficulty if the prostatic nature of the epithelium is not appreciated, an error that is likely if a relationship to the prostate is not recognized. This lesion should be included in the differential diagnosis of retroperitoneal cystic tumors in men.

A 51-year-old man was found to have two separate intratesticular serous cystadenomas of low malignant potential. Electron microscopy and OC 125 antibody reactivity characterize the neoplasms as serous and suggest müllerian histogenesis.

Microcystic adenoma (serous cystadenoma) of the pancreas (MA) is an unusual benign tumor of uncertain histogenesis. We have studied 14 cases of MA from 11 women and three men. The average age at diagnosis was 64 years. Six tumors were discovered incidentally. Tumors varied from 2.5 to 12 cm in greatest dimension and all were multicystic; eight tumors were located in the pancreatic head, two in the body, and three in the tail. Each tumor was composed of variably sized cysts lined by simple cuboidal or flattened, focally glycogen-rich epithelium. The stroma was variably collagenized and showed highly vascularized, delicate to broad fibrous septae, which focally contained dystrophic calcification, cholesterol clefts, and hemosiderin. Immunohistochemical studies were performed on eight cases to determine the cell of origin. Epithelial membrane antigen and a low-molecular-weight keratin, detected by monoclonal antibodies PKK1 or AE1/AE3, were diffusely seen in tumor cells of all cases. Tumor cells were uniformly negative for carcinoembryonic antigen, chromogranin, insulin, glucagon, somatostatin, vasoactive intestinal peptide, pancreatic polypeptide, and a low-molecular-weight keratin detected by monoclonal antibody PKK2. Tumor cell antigen reactivity most resembled that seen in normal centroacinar and ductal cells. Electron microscopy of seven cases showed primitive tumor cells with irregularly spaced, short, blunt microvilli, luminal occluding junctions and belt desmosomes, bundles of filaments including dense bodies in both apical and basal cell cytoplasm, sparse organelles, and variable but often pronounced amounts of glycogen. These ultrastructural features most closely resembled the normal pancreatic centroacinar cell. Based on both immunohistochemical and ultrastructural features described above, we conclude that the centroacinar cell is the cell of origin of MA.

A cystic tumor composed of atypical glands in a cellular stroma arose in the pelvis of a 49-year-old man. Two years later an identical tumor was again excised from the pelvis. Morphologic, immunohistochemical and ultrastructural studies indicate that this neoplasm arose in the seminal vesicle, possibly from a seminal vesicle cyst. The tumor did not involve the prostate gland, and immunohistochemical stains for prostate-specific antigen and prostatic acid phosphatase were negative. Ultrastructural study showed that both the glandular and mesenchymal components of the tumor recapitulated features of normal seminal vesicle, further establishing origin from this site. This tumor resembles the rare cystadenoma of the seminal vesicle, yet the cytologic atypia suggests low grade malignant potential. Following the second excision, the patient has had a disease-free interval of 18 months. Long term follow-up and recognition of additional cases is necessary to define the biologic potential of this unusual tumor.

Microcystic adenomas are rare tumors, which have only recently been distinguished from other cystic pancreatic lesions. This study details eight cases diagnosed at the Cleveland Clinic. Seven occurred in females. The mean age at diagnosis was 66 years. Abdominal or epigastric pain was the most common symptom. A history of extrapancreatic tumors was frequent, and one patient had a concomitant renal carcinoma with adrenal and renal cysts. The adenomas were multicystic, ranging in size from 2 to 14 cm. Cuboidal epithelial cells with vacuolated or clear cytoplasm containing abundant glycogen lined the cysts. The intervening stromal septa were collagenous and hypocellular. The epithelial cells exhibited strongly positive immunostaining for cytokeratins AE1 and AE3, but did not stain with CEA and Uro-2,3, and 4. Ultrastructurally, the epithelial cells rested on well-formed basal lamina and a delicate subepithelial capillary network. They had blunted apical microvilli and contained glycogen, few lipid droplets, and occasional apical secretory granules. Five adenomas were resected, and three had only a diagnostic biopsy. There were no metastases, but one patient died of postoperative complications following local excision. Elderly or high-risk patients may benefit more from biopsy alone than from attempts at total surgical resection of these benign tumors.