Cutaneous myoepithelial neoplasms are a heterogenous group of neoplasms with mixed tumors typically affecting the head and myoepitheliomas showing a predilection for the extremities. Their malignant counterparts, myoepithelial carcinoma, and malignant mixed tumor are exceptionally rare in the skin, and the morphologic criteria for malignancy are only poorly defined. The aim of the present study was to characterize the clinicopathologic features of myoepithelial neoplasms presenting on acral skin. The clinical and histopathologic features of 11 tumors were recorded, and follow-up was obtained. Immunohistochemistry was performed for S100, SOX10, glial fibrillary acidic protein, keratins, epithelial membrane antigen, p63, p40, smooth muscle actin, desmin, and PLAG1. The tumors mainly affected the feet of adults (range: 26 to 78 y; median: 47 y) with a predilection for the great toe and a male predominance of 1.8:1. Most tumors (91%) displayed a lobular architecture composed of solid and nested growth of epithelioid cells with plasmacytoid features in a myxoid or angiomatous stroma. Scattered cytologic atypia and rare duct differentiation were frequently noted. Three tumors with confluent cytologic atypia, infiltrative growth, and lymphovascular invasion were classified as malignant. By immunohistochemistry, the tumors were positive for S100, SOX10, keratins AE1/AE3, CK5/6 and CK7, and PLAG1. Local recurrence and bilateral pulmonary metastasis were observed in a patient presenting with a histopathologically benign-appearing tumor. Two patients with malignant tumors experienced local recurrences, and 1 developed metastasis to soft tissue, lung, and mediastinal lymph nodes. All patients are currently alive, all but 1 with no evidence of disease after a median follow-up interval of 96 months (range: 2 to 360 mo). In conclusion, acral myoepithelial neoplasms show distinctive and reproducible histopathologic and immunohistochemical features. They are best regarded as a distinctive subset of mixed tumors with features reminiscent of their salivary gland counterparts. While most tumors pursue a benign disease course, histopathologic features appear to be a poor indicator of prognosis.

皮肤肌上皮肿瘤是一组异质性肿瘤，混合肿瘤通常累及头部，肌上皮瘤好发于四肢。它们的恶性对应物，肌上皮癌和恶性混合瘤在皮肤中极为罕见，并且恶性肿瘤的形态学标准仅定义不明确。本研究的目的是描述出现在肢端皮肤上的肌上皮肿瘤的临床病理学特征。记录11个肿瘤的临床和组织病理学特征，并进行随访。免疫组织化学对 S100、SOX10、胶质纤维酸性蛋白、角蛋白、上皮膜抗原、p63、p40、平滑肌肌动蛋白、结蛋白和 PLAG1 进行了检测。肿瘤主要影响成年人的足部（范围：26 至 78 岁；中位数：47 岁），好发于大脚趾，男性占 1.8:1。大多数肿瘤 (91%) 显示小叶结构，由实性和嵌套生长的上皮样细胞组成，在粘液样或血管瘤基质中具有浆细胞样特征。经常注意到散在的细胞学异型性和罕见的导管分化。三个具有融合细胞学异型性、浸润性生长和淋巴血管侵犯的肿瘤被归类为恶性。通过免疫组织化学，肿瘤对 S100、SOX10、角蛋白 AE1/AE3、CK5/6 和 CK7 以及 PLAG1 呈阳性。一名组织病理学表现为良性肿瘤的患者出现局部复发和双侧肺转移。2例恶性肿瘤患者局部复发，1例发生软组织、肺和纵隔淋巴结转移。目前所有患者都还活着，除了 1 名患者在 96 个月的中位随访间隔（范围：2 至 360 个月）后没有任何疾病证据。总之，肢端肌上皮肿瘤表现出独特且可重复的组织病理学和免疫组织化学特征。它们最好被视为混合肿瘤的一个独特子集，其特征让人联想到唾液腺对应物。虽然大多数肿瘤都追求良性病程，