Thway Khin, Noujaim Jonathan, Thomas D Michael, Fisher Cyril, Jones Robin L
Sarcoma Unit, Royal Marsden NHS Foundation Trust, London.
Department of Cellular Pathology, Maidstone and Tunbridge Wells NHS Trust, Kent, UK.
Rare Tumors. 2017 Mar 31;9(1):6504. doi: 10.4081/rt.2017.6504. eCollection 2017 Mar 24.
Myoepithelial tumors of the soft tissues represent a rare group of neoplasms that vary in their clinical behavior, pathologic features and genetics. They are histopathologically typified by a immunohistochemical phenotype, of expression of one or more epithelial markers, S100 protein and smooth muscle actin. Because of their rarity and occurrence over a wide age range and at a variety of anatomic sites, they can be difficult to diagnose due to the lack of familiarity by physicians, which is compounded by their spectrum of histologic features and morphologic overlap with several other neoplasms. Recent genetic insights have aided classification, and it is increasingly understood that soft tissue myoepithelial neoplasms can be stratified into two distinct morphologic and genetic subgroups. We describe a case of a 44-year-old man who was diagnosed with a primary myoepithelial neoplasm of the paracecal mesentery, which showed aggressive local recurrence after four years. The tumor was composed of cords of ovoid cells within chondromyxoid stroma, and displayed a characteristic pancytokeratin, S100 protein and smooth muscle actin-positive immunoprofile. Primary myoepithelioma has not been previously described at this site, and this case highlights this varied family of tumors, emphasizes the need to consider myoepithelial tumor in the differential diagnoses of carcinoma variants occurring in the bowel or mesentery, and also adds to the number of reported myoepithelial neoplasms showing markedly aggressive behavior.
软组织肌上皮肿瘤是一组罕见的肿瘤，其临床行为、病理特征和遗传学各不相同。它们在组织病理学上的典型特征是免疫组化表型，即表达一种或多种上皮标志物、S100蛋白和平滑肌肌动蛋白。由于其罕见性，发病年龄范围广，且发生于多种解剖部位，医生对其缺乏了解，再加上其组织学特征谱以及与其他几种肿瘤的形态学重叠，使得它们难以诊断。最近的遗传学见解有助于分类，并且人们越来越认识到软组织肌上皮肿瘤可分为两个不同的形态学和遗传学亚组。我们描述了一例44岁男性，他被诊断为盲肠旁系膜原发性肌上皮肿瘤，4年后出现侵袭性局部复发。肿瘤由软骨黏液样基质内的卵圆形细胞索组成，并表现出特征性的全细胞角蛋白、S100蛋白和平滑肌肌动蛋白阳性免疫表型。此前尚未有原发性肌上皮瘤在该部位的报道，该病例突出了这类多样的肿瘤，强调在肠道或系膜发生的癌变体的鉴别诊断中需要考虑肌上皮肿瘤，同时也增加了显示明显侵袭性行为的报道的肌上皮肿瘤的数量。
