The WHO Classification of Tumors of Soft Tissue and Bone divides rhabdomyosarcoma (RMS) into alveolar, embryonal, pleomorphic, and spindle cell/sclerosing types. Advances in molecular diagnostics have allowed for further refinement of RMS classification including the identification of new subtypes. Very rare RMS with epithelioid and spindle cell morphology, female predominance, marked osseous predilection, ALK expression, EWSR1/FUS-TFCP2 gene fusions, and highly aggressive clinical behavior have recently been recognized with only 23 cases reported in the English language literature. Herein, we report two additional cases with detailed clinicopathologic description and molecular confirmation. In brief, two young women presented each with a primary bone tumor—one with a frontal bone tumor and another with an osseous pelvic tumor. Both tumors showed epithelioid to spindle cell morphology, ALK expression, and EWSR1/FUS-TFCP2 gene fusions. Both patients died of disease less than 17 months from diagnosis despite administration of multiple lines of aggressive treatment. In addition, we review the literature and discuss differential diagnostic and potential treatment considerations.

WHO的软组织和骨肿瘤分类将横纹肌肉瘤（RMS）分为肺泡型，胚胎型，多形性和梭形细胞/硬化型。分子诊断学的进步允许进一步细化RMS分类，包括鉴定新的亚型。RMS非常罕见，具有上皮样和纺锤状细胞形态，女性占优势，明显骨性病变，ALK表达，EWSR1 / FUS-TFCP2基因融合和高度侵略性的临床行为最近在英语文献中仅报道23例。在此，我们报告了另外两个病例，并进行了详细的临床病理描述和分子确认。简而言之，两名年轻妇女各自患有原发性骨肿瘤-一名患有额骨肿瘤，另一名患有骨盆骨肿瘤。两种肿瘤均显示上皮样到纺锤体细胞的形态，ALK表达和EWSR1 / FUS-TFCP2基因融合。尽管进行了多系积极治疗，但两名患者均在诊断后不到17个月死于疾病。另外，我们回顾了文献并讨论了鉴别诊断和潜在治疗的考虑。