结肠髓样癌2例临床病理观察

Clinicopathologic features of medullary carcinoma of the colon:a report of 2 cases

目的探讨结肠髓样癌的临床病理学及分子遗传特征,诊断与鉴别诊断。方法回顾性分析2例结肠髓样癌,总结其临床、组织学、免疫表型、微卫星不稳定状态及B-RAF基因突变EBER原位杂交,并结合相关文献进行讨论。结果 2例患者均为女性,年龄分别为81、87岁,发生部位均位于回盲部。组织学上,2例病变形态相似,肿瘤细胞呈实体条索状、巢状排列;癌细胞较大,圆形、卵圆形或多边形;可见嗜酸性胞质,核大,核仁明显,可见囊胞状核。肿瘤间质内大量淋巴细胞浸润。免疫组化示肿瘤细胞不表达肠源性标记CDX2、CK20,错配修复蛋白MLH1/PMS2(-),MSH2/MSH6(+),分子检测B-RAF基因V600E突变。EBER均(-)。结论结肠髓样癌是一种罕见的肠道低分化上皮性肿瘤,具有相对独特的组织学、免疫表型及分子遗传学特征。与肠道其他低分化或未分化肿瘤相比,结肠髓样癌具有相对较好的预后。

Objective To study the clinicopathological features, molecular characteristics, differential diagnosis of medullary carcinoma of the colon. Methods Two cases of poorly differentiated large bowel carcinomas were identified as medullary carcinoma. Clinical data, histological appearance, immunophenotype, molecular characteristics and EBEV status were observed, and the related literatures were reviewed. Results Two eases of medullary carcinoma were old women, aged 81 and 87 years, respectively. Both tumors were located in the ileocecal region. Microscopically, the neoplastic cells showed a solid nested, organoid and trabeeular growth pattern. Tumors often contained higher amounts of tumor-infiltrating lymphocytes as a distinguishing feature. Tumor cells were large round to oval nuclei, with amphophilic nucleoli, and vesicular chromatin. Immunohistochemical reactions were negative for CDX2 and CK20. Mismatch repair protein MLH1/ PMS2 was negative, and MSH2/MSH6 positive. The tumor showed B-RAF gene V600E mutation and negative EBER in tumor cells. Conclusions Medullary carcinoma of the colon is a rare and unique subtype of colorectal carcinoma, which represents a distinct pathologic entity, with specific histological appearance and peculiar clinical and genetic features. It needs to be classified separately from other poorly differentiated colorectal carcinomas, which has better survival as compared with others colorectal carcinoma.