原发性皮肤肉瘤样鳞状细胞癌可表现出与其他恶性梭形细胞肿瘤显着的组织学重叠，这给诊断带来了挑战。即使有多种免疫组织化学标记物，在某些情况下，识别准确的分化系也可能是一个挑战。这些肿瘤导致肌纤维母细胞标记物 [例如平滑肌肌动蛋白 (SMA)] 的异常表达，以及随之而来的传统上皮标记物的丧失，使情况变得更加复杂。原发性皮肤肉瘤样鳞状细胞癌的组织学鉴别诊断包括促纤维增生性黑色素瘤、平滑肌肉瘤和梭形细胞非典型纤维黄瘤/多形性真皮肉瘤（AFX/PDS）。对从大型学术机构获得的 16 例具有 SMA 表达的 PCSSCC 病例进行了回顾性分析，总结如下。肿瘤部位为头皮（6例）、手臂（4例）、腿部（2例）、面部（2例）、手（1例）、颈部（1例）。使用以下抗体对所有病例进行免疫组织化学研究：AE1/AE3、CAM 5.2、MNF-116、p63、p40、CK5/6、S-100、SOX10、SMA、结蛋白、钙调蛋白、H-caldesmon、CD10、CD68 、CD163 和 CD34。组织病理学上，所有病例均被归类为高级别恶性低分化肿瘤。肿瘤的特点是浸润性肿瘤，累及整个网状真皮，其中 7 例累及皮下脂肪。三个病例与分化良好的鳞状细胞成分相关。肿瘤由排列成长且交叉的束状的非典型纺锤体和上皮样细胞组成。所有肿瘤的上皮标记物（至少 1 种标记物）均呈阳性，并且所有病例的 SMA 均呈强阳性。我们的数据强调了多种上皮标记物作为检测和检查恶性皮肤肉瘤样肿瘤的第一个筛查工具的诊断效用。了解这些肿瘤中的 SMA 表达可能会使诊断变得复杂，认识到这种异常的免疫表型对于促进明确诊断并避免误诊非常重要。版权所有 © 2024 Wolters Kluwer Health, Inc. 保留所有权利。

Primary cutaneous sarcomatoid squamous cell carcinoma can show significant histologic overlap with other malignant spindle cell tumors, posing a diagnostic challenge. Even with a wide array of immunohistochemical markers, the exact line of differentiation can be a challenge to identify in some cases. The picture is further complicated by the aberrant expression of myofibroblastic markers [such as smooth muscle actin (SMA)] by these neoplasms, along with a concomitant loss of conventional epithelial markers. The histologic differential diagnoses of primary cutaneous sarcomatoid squamous cell carcinoma include desmoplastic melanoma, leiomyosarcoma, and spindle cell atypical fibroxanthoma/pleomorphic dermal sarcoma (AFX/PDS). A retrospective analysis of 16 cases of PCSSCCs with SMA expression, obtained from large academic institutions, was performed and is summarized below. The tumors were in the scalp (6 cases), arm (4 cases), leg (2 cases), face (2 cases), hand (1 case), and neck (1 case). Immunohistochemical studies were performed in all cases with the following antibodies: AE1/AE3, CAM 5.2, MNF-116, p63, p40, CK5/6, S-100, SOX10, SMA, desmin, calponin, H-caldesmon, CD10, CD68, CD163, and CD34. Histopathologically, all cases were classified as high-grade malignant poorly differentiated neoplasms. Tumors were characterized by an infiltrative neoplasm that involved the entire reticular dermis and, in 7 cases, the subcutaneous fat. Three cases were associated with a well-differentiated squamous cell component. The neoplasms were composed of atypical spindle and epithelioid cells arranged in long and intersecting fascicles. All neoplasms were positive for epithelial markers (at least 1 marker), and all cases were strongly positive for SMA. Our data emphasize the diagnostic utility of multiple epithelial markers as a first screening tool in the detection and workup of malignant cutaneous sarcomatoid neoplasms. Awareness of SMA expression in these tumors can complicate its diagnosis, and it is important to recognize this aberrant immunophenotype to facilitate definitive diagnosis and avoid misdiagnosis.Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.