Primary Gastric Melanoma with Rhabdoid Features: A Case Report

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Malignant melanomas display a wide variety of morphologic patterns. 1 Melanomas with rhabdoid appearance are rare and appear mostly as a recurrent or metastatic form, and only atypi-cally arise as a primary lesion. Just eight cases of primary rhab-doid melanomas can be found in the literature since 1994. 2-7 Malignant melanomas frequently metastasize to the gastroin-testinal tract; they can be located in the stomach and are generally metastases of cutaneous melanomas. Primary gastric mela-nomas are extremely rare, and, to the best of our knowledge, a primary melanoma with rhabdoid features has not been reported thus far. Here, we report a case of primary gastric melanoma with rhabdoid features along with its immunohistochemical panels and ultrastructural findings. A 59-year-old male presented with a gastric mass that was found incidentally on gastroesophagoscopy. The only relevant history was a recent cerebral hemorrhage that occurred three months prior. Endoscopically, the mass was polypoid in appearance at the posterior wall of the fundus (Fig. 1). Stomach computed tomography showed an enhancing mass measuring 4.0 cm in diameter with central necrotic change at the cardia, and one enlarged regional lymph node, measuring 1.0 cm in diameter , posterior to the cardia. Under the impression of gastric car-cinoma, total gastrectomy was performed. Preoperative endo-scopic biopsy was not undertaken. A fungating grayish-tan colored mass was found at the posterior wall of the cardia, involving the esophagogastric junction. The cut surface of the polyp-oid mass revealed a homogeneous grayish-tan in appearance with focal hemorrhagic changes and focal mucosal ulcer. The mass invaded mucosa, submucosa, and inner proper muscle. It extended to the esophagogastric junction. Histologically, a solid growth pattern and pseudoalveolar clefts were found (Fig. 2A). The mass was infiltrated by round, small-to-large-sized cells with plump eosinophilic cytoplasm and peripherally compressed nuclei, creating an occasional rhabdoid appearance. The tumor cells had an irregular shape with angulated nuclei, irregular nuclear contours, and fine chromatin. Occasional marked pleomor-phic cells were found. Mitotic figures were counted up to 15/10 high power fields. Metastatic foci were demonstrated in one of 20 regional lymph nodes. The observed normal-appearing gastric and esophageal mucosa showed no abnormalities. Under the impression of malignant melanoma, gastrointestinal stromal tumor , poorly differentiated …