[Three Cases of Colon Medullary Carcinoma in Our Institution].

Medullary carcinoma of the colorectum is a relatively new histological subtype that was first described in the eighth edition of the Japanese classification of colorectal, appendiceal, and anal carcinoma. In our institution, only 3 cases of medullary carcinoma have been diagnosed since 2013. Case #1 was a 93-year-old woman with type 1 ascending colon cancer; she received a right hemicolectomy. The tumor invaded the subserosal layer, but no lymph nodal metastasis was observed. Case #2 was a 91-year-old woman with obstructive ascending colon cancer. After intracolonic decompression using the transnasal ileus tube, she received a right hemicolectomy. This tumor also extended into the subserosal layer without lymph nodal metastasis. Case #3 was a 65-year-old woman with a family history of cancers; she received a right hemicolectomy for cecal cancer with an aberrant elevation of serum tumor markers such as CEA and CA19-9. The tumor invaded the subserosal layer with regional lymph nodal metastases. Notably, these 3 cases were females who had right-sided tumors and all showed diminished expressions of MLH1 and PMS2 mismatch repair-associated genes, together with epidemiological characteristics of medullary carcinoma. Herein, we report their pathological features along with the corresponding literature review.