Harada Oi, Ota Hiroyoshi, Nakayama Jun
Department of Pathology, Shinshu University School of Medicine, Matsumoto, Nagano, Japan.
Pathol Int. 2005 Aug;55(8):510-3. doi: 10.1111/j.1440-1827.2005.01861.x.
Malignant myoepithelioma of soft tissue is extremely rare. Presented herein is a case arising in a 17-year-old man. The tumor was initially noticed as a painless deep soft-tissue mass in the right forearm when the patient was aged 3 years. Thereafter, it grew without remarkable symptoms, such as pain or tenderness, until his visit to the hospital because of swelling of his forearm when he was 17 years old. An excisional biopsy specimen disclosed an invasive tumor exhibiting a lobular architecture. The tumor cells were arranged in a reticular and/or trabecular fashion with a myxoid background, and nuclear atypia was evident. Mitoses and tumor necrosis were also observed. Immunohistochemically, S-100 protein and epithelial markers were diffusely positive. Faint intercellular junctions and basal laminae were identified by electronmicroscopy. On the basis of these findings, the tumor was diagnosed as a malignant myoepithelioma of soft tissue. Six months later, multiple lung metastases were observed, and an open biopsy revealed a neoplasm displaying the same histological feature as the previously biopsied specimens. The patient died of his disease 18 months after the lung biopsy. Malignant myoepithelioma should be kept in mind in diagnosis of deep soft-tissue tumors with epithelioid features.
软组织恶性肌上皮瘤极为罕见。本文报告1例发生于一名17岁男性的病例。该肿瘤最初在患者3岁时被发现为右前臂一个无痛性深部软组织肿块。此后，它在无疼痛或压痛等明显症状的情况下生长，直至17岁时因前臂肿胀前来就诊。切除活检标本显示为一个具有小叶结构的浸润性肿瘤。肿瘤细胞呈网状和/或小梁状排列，伴有黏液样背景，核异型明显。还观察到有丝分裂和肿瘤坏死。免疫组织化学检查显示，S-100蛋白和上皮标志物弥漫性阳性。电镜检查发现有微弱的细胞间连接和基膜。基于这些发现，该肿瘤被诊断为软组织恶性肌上皮瘤。6个月后，观察到多发肺转移，开放活检显示肿瘤具有与先前活检标本相同的组织学特征。肺活检18个月后患者死于该疾病。在诊断具有上皮样特征的深部软组织肿瘤时应考虑到恶性肌上皮瘤。
