Herein, we report a rare case of a carcinoma with primitive phenotype (enteroblastic and/or hepatoid differentiation) occurring at a colostomy site. The patient was an elderly male who underwent neoadjuvant chemoradiotherapy for rectal cancer, followed by abdominoperineal resection. A biopsy specimen for the rectal carcinoma before neoadjuvant chemoradiotherapy was conventional tubular adenocarcinoma. Moreover, a pathological complete response was confirmed in the proctectomy specimen. However, a colostomy-site tumor appeared 6 months after the proctectomy, and it was resected 1 year after the initial proctectomy. The colostomy-site tumor comprised solid to focal glandular growth of atypical polygonal cells with clear to pale eosinophilic cytoplasm and was immunohistochemically positive for cytokeratin, spalt-like transcription factor 4, glypican-3, caudal type homeobox 2, and special AT-rich sequence-binding protein 2. Thus, the tumor was diagnosed as poorly differentiated adenocarcinoma with primitive phenotype, with suggested origin from the colorectal epithelium. Additionally, a multilocular cystic lesion comprising various types of epithelia was found adjacent to the tumor, suggestive of metaplasia or heterotopia. Changes in the histology and immunophenotype, and the findings of an adjacent cystic lesion suggest a metachronous tumor rather than a recurrence of the primary tumor.

中文翻译：

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直肠癌患者新辅助放化疗达到病理完全缓解后出现原始表型结肠造口癌

在此，我们报告一例罕见的结肠造口部位发生的具有原始表型（肠母细胞和/或肝样分化）的癌症。该患者是一名老年男性，接受了直肠癌新辅助放化疗，随后进行了腹会阴切除术。新辅助放化疗前直肠癌活检标本为常规管状腺癌。此外，在直肠切除标本中证实了病理学完全缓解。然而，直肠切除术后6个月出现结肠造口部位肿瘤，并在初次直肠切除术后1年被切除。结肠造口部位肿瘤由非典型多边形细胞实性到局灶性腺体生长组成，细胞质清晰至苍白，细胞角蛋白、spalt 样转录因子 4、磷脂酰肌醇蛋白聚糖 3、尾部型同源框 2 和富含 AT 的特殊序列免疫组织化学呈阳性。 -结合蛋白2。因此，肿瘤被诊断为具有原始表型的低分化腺癌，提示起源于结直肠上皮。此外，在肿瘤附近发现了包含各种类型上皮的多房性囊性病变，提示化生或异位。组织学和免疫表型的变化以及邻近囊性病变的发现表明异时肿瘤而不是原发肿瘤的复发。