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The authors report a 69-year-old man with a primary nodular malignant melanoma on the shoulder showing unusual histological features. It mostly consisted of markedly neoplastic melanocytes, which exhibited abundant clear cytoplasm compressing the nuclei to the periphery, resulting in a signet-ring appearance. In other areas of the melanoma, there were focally desmoplastic and pseudoglandular patterns and oncocytoid changes. Immunohistochemical studies showed that the tumor cells were uniformly positive only for S-100 protein and vimentin. Signet-ring cell melanoma is a rare histopathological variant of malignant melanoma with only a few described cases. To the best of our knowledge, this is the first case reporting a combination of the signet-ring cell melanoma with desmoplastic, pseudoglandular, and oncocytoid features.

We report two cases of a previously unrecognized neoplasm, each characterized by prominent lobular configuration in the subcutaneous tissue. Within the neoplasms were distinctive garland-shaped structures composed of glial fibrillary acidic protein (GFAP) positive cells with indistinct borders, encased in concentric loops of fine collagen fibers. In some areas, the neoplastic cells were distributed in small lacunae. The extracellular space between the collagenous tissue and the cells was filled with copious myxoid matrix. One of the neoplasms also demonstrated areas with spindle cells which resembled leiomyoma. Immunohistochemistry was negative for smooth muscle actin (1A4), muscle actin (HHF35), S-100 protein, desmin, cytokeratin, KP1, and epithelial membrane antigen (EMA.) Currently, both patients are free of recurrence or metastasis 2 and 4 years after primary surgical excision. The neoplasms, which we term benign polymorphous mesenchymal tumor of soft parts (BPMT), should be distinguished from ossifying fibromyxoid tumor of soft parts, extraskeletal mesenchymal chondrosarcoma, neoplasms arising in ectopic breast tissue and mixed tumor of the skin.

An unusual low-grade metaplastic carcinoma (mullerian carcinosarcoma) of the uterine corpus occurring in a 45-year-old woman is presented. The tumor was polypoid and showed an initial invasion into the myometrium. The epithelial component was composed of low-grade endometrioid glands that focally showed an unusual oxyphilic change of the cytoplasm. These cells contained only a small amount of mitochondria detected with antimitochondrial antibody. The stromal component contained small round cells of bland appearance and appeared to arise from epithelial cells through a metaplastic process, as a gradual transition between epithelial and stromal cells was often seen. An invasive marginal zone of the tumor showed endometrioid adenocarcinoma pattern without any stromal component. The proliferative activity generally was low. Interestingly, it was clearly accentuated in the epithelial component especially in the peripheral invasive areas, whereas it was very low in the stromal component. The course of disease was indolent. Low-grade mullerian carcinosarcoma is to be distinguished from other biphasic mullerian tumors.