Jo Vickie Y, Fletcher Christopher D M
Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA, 02115, USA.
Head Neck Pathol. 2015 Mar;9(1):32-8. doi: 10.1007/s12105-015-0618-0. Epub 2015 Mar 25.
Myoepithelial tumors in skin and soft tissue are uncommon but have been increasingly characterized over the past decade. Men and women are equally affected across all age groups and lesions arise most frequently on the extremities and limb girdles. Approximately 20 % of cases occur in pediatric patients, in whom they are frequently malignant. Similar to their salivary gland counterparts, myoepithelial tumors of soft tissue demonstrate heterogeneous morphologic and immunophenotypic features. Tumors are classified as mixed tumor/chondroid syringoma, myoepithelioma, and myoepithelial carcinoma; in soft tissue, tumors having at least moderate cytologic atypia are classified as malignant. Mixed tumor and myoepithelioma show a benign clinical course, with recurrence in up to 20 % (typically secondary to incomplete excision), and do not metastasize. In contrast, myoepithelial carcinoma shows more aggressive behavior with recurrence and metastasis in up to 40-50 % of cases. The majority of myoepithelial neoplasms typically coexpress epithelial antigens (cytokeratin and/or EMA) and S-100 protein; GFAP and p63 are frequently positive and a subset of malignant neoplasms lose INI1 expression. Up to 45 % of myoepitheliomas and myoepithelial carcinomas harbor EWSR1 gene rearrangements, unlike mixed tumor/chondroid syringoma which is characterized by PLAG1 gene rearrangement. While mixed tumor/chondroid syringoma are likely related to primary salivary myoepithelial tumors, soft tissue myoepithelioma and myoepithelial carcinoma appear to be pathologically distinct neoplasms.
皮肤和软组织中的肌上皮肿瘤并不常见，但在过去十年中其特征越来越明确。所有年龄组的男性和女性受影响程度相同，病变最常出现在四肢和肢体带。约20%的病例发生在儿科患者中，这类肿瘤在儿科患者中常为恶性。与涎腺的同类肿瘤相似，软组织肌上皮肿瘤表现出形态学和免疫表型特征的异质性。肿瘤分为混合瘤/软骨样汗腺腺瘤、肌上皮瘤和肌上皮癌；在软组织中，具有至少中度细胞学异型性的肿瘤被分类为恶性。混合瘤和肌上皮瘤表现为良性临床病程，复发率高达20%（通常继发于切除不完全），且不发生转移。相比之下，肌上皮癌表现出更具侵袭性的行为，高达40 - 50%的病例会复发和转移。大多数肌上皮肿瘤通常共表达上皮抗原（细胞角蛋白和/或EMA）和S - 100蛋白；GFAP和p63常呈阳性，一部分恶性肿瘤会丢失INI1表达。高达45%的肌上皮瘤和肌上皮癌存在EWSR1基因重排，这与以PLAG1基因重排为特征的混合瘤/软骨样汗腺腺瘤不同。虽然混合瘤/软骨样汗腺腺瘤可能与原发性涎腺肌上皮肿瘤相关，但软组织肌上皮瘤和肌上皮癌在病理上似乎是不同的肿瘤。
