Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
Am J Surg Pathol. 2011 Oct;35(10):1523-30. doi: 10.1097/PAS.0b013e31822e0907.
Rhabdomyosarcoma (RMS), which affects mainly pediatric patients, is currently classified into 3 major categories: embryonal, alveolar, and pleomorphic. We have identified a distinct variant of RMS that is characterized by epithelioid morphology, reminiscent of poorly differentiated carcinoma or melanoma, for which we propose the designation "epithelioid RMS." We examined the clinicopathologic features of 16 such cases, which were received in consultation between 1991 and 2009. Ten patients were men, and 5 were women (gender was unknown in 1 case), with a median age of 70.5 years (range 14 to 78). Primary anatomic sites were upper extremity (4), lower extremity (2), head and neck (3), trunk (3), hypopharynx (1), and left atrium (1). Two patients presented with nodal metastases (neck and mediastinal) with unknown primary sites. Of the tumors in somatic locations, 10 were intramuscular, and 2 were subcutaneous. Tumor size ranged from 3 to 8.5 cm; the tumors had nodular fleshy cut surfaces, grossly appreciable necrosis, and infiltrative edges. Microscopically, tumors showed sheet-like growth of uniformly sized epithelioid cells with abundant amphophilic-to-eosinophilic cytoplasm, large vesicular nuclei, and frequently prominent nucleoli. Necrosis and infiltration into adjacent structures (such as skeletal muscle or fat) were present in all cases, and mitotic counts were high (median count 23 per 10 high-power fields) with frequent atypical forms. By immunohistochemistry, all tumors showed diffuse desmin expression, and myf-4 immunostaining was diffuse to multifocally positive. S100-protein was absent in all cases. Cytokeratin was negative in 12 cases and very focally positive in 4 cases. Clinical follow-up information was available for 11 cases (median duration 10 mo). Most patients underwent surgical resection with chemotherapy and/or radiation (none with RMS-specific protocols). Two patients had multiple recurrences, and 2 patients developed satellite nodules near the primary lesion. Six patients had regional lymph node metastases, and 6 patients developed distant metastases, most commonly to the lung. So far, 7 patients have died of disease, 5 within 1 year and 2 within 5 years. Epithelioid RMS is a novel morphologically distinct variant of RMS that closely mimics carcinoma or melanoma. It primarily affects older patients, with a male predilection. The clinical course as determined thus far is aggressive.
横纹肌肉瘤（RMS）主要影响儿科患者，目前分为 3 个主要类别：胚胎性、肺泡性和多形性。我们已经确定了一种独特的 RMS 变体，其特征为上皮样形态，类似于低分化癌或黑色素瘤，我们建议将其命名为“上皮样 RMS”。我们研究了 16 例此类病例的临床病理特征，这些病例是在 1991 年至 2009 年期间会诊时收到的。10 名患者为男性，5 名患者为女性（1 例患者性别不明），中位年龄为 70.5 岁（范围为 14 岁至 78 岁）。主要解剖部位为上肢（4 例）、下肢（2 例）、头颈部（3 例）、躯干（3 例）、下咽（1 例）和左心房（1 例）。2 例患者出现淋巴结转移（颈部和纵隔），原发灶不明。位于躯体部位的肿瘤中，10 例为肌内肿瘤，2 例为皮下肿瘤。肿瘤大小为 3 至 8.5 厘米；肿瘤呈结节状，肉质切面，肉眼可见明显坏死和浸润性边缘。显微镜下，肿瘤呈均匀大小的上皮样细胞片状生长，胞浆丰富，嗜酸性至嗜碱性，细胞核大，常有明显核仁。所有病例均有坏死和浸润相邻结构（如骨骼肌或脂肪），核分裂计数高（中位数每 10 个高倍视野 23 个），常伴有非典型形态。免疫组织化学染色显示，所有肿瘤均弥漫表达结蛋白，myf-4 免疫染色弥漫至多灶性阳性。所有病例 S100 蛋白均阴性。12 例肿瘤细胞角蛋白阴性，4 例肿瘤细胞角蛋白局灶性弱阳性。11 例患者可获得临床随访信息（中位随访时间 10 个月）。大多数患者接受了化疗和/或放疗的手术切除（无 RMS 特异性方案）。2 例患者出现多次复发，2 例患者在原发灶附近出现卫星结节。6 例患者出现区域淋巴结转移，6 例患者出现远处转移，最常见于肺部。迄今为止，7 例患者死于疾病，其中 5 例在 1 年内，2 例在 5 年内。上皮样 RMS 是一种形态学上独特的 RMS 变体，与癌或黑色素瘤非常相似。它主要影响老年患者，男性居多。迄今为止确定的临床病程是侵袭性的。
