Malignant rhabdoid tumor of the colon: a case report.

Malignant rhabdoid tumors are highly aggressive neoplasms that were initially described in the kidneys of children as a rare variation of Wilms tumors with a rhabdomyosarcomatoid pattern and particularly poor prognosis. Subsequently, tumors with histologically similar characteristics were found in other locations, and classified as extrarenal malignant rhabdoid tumors (EMRT). These neoplasms are rare and have a very aggressive behavior. Their origin has been debated, as they have been described in several solid organs. To date, only 43 cases have been reported in the gastrointestinal tract, 5 the esophagus, 16 the stomach, 10 the small bowel and 12 the colon. We present the case of a 77-year-old male with a prior history of ischemic cardiopathy who reported having abdominal pain and rectal bleeding over the course of the previous month. Colonoscopy revealed a stenosing neoformation with partial necrosis that was 78 cm from the anal margin. Biopsy demonstrated the presence of atypical cells compatible with carcinoma, although immunohistochemistry showed negativity of the tumor cells for CDx-2 and CK 20, which suggested a non-colonic origin. Pre-operative CT showed no evidence of distant disease (Fig. 1). During surgery, a large tumor was found in the descending colon that infiltrated the omentum and parietal peritoneum; a left hemicolectomy with primary anastomosis and resection of the affected abdominal wall was performed. The pathology study determined the lesion was a high-grade infiltrating malignant neoplasm (pT4aN1bMx), with co-expression of cytokeratin cocktail and vimentin (Fig. 2A and B), with negative CK7 and CK20, CDx2 ( ), ALC ( ), desmin ( ), BerEP4 ( ), p53 ( ), CD117 ( ) and calretinin ( ), compatible with primary rhabdoid tumor of the colon. On the 7th day post-op, the patient needed a reoperation due to anastomotic leak, which included resection of the anastomosis and terminal colostomy in the left lower quadrant. The patient’s postoperative recovery was slow and required a stay in the ICU. One month after the initial intervention, a follow-up CT reported several mediastinal and retroperitoneal lymphadenopathies. In addition, in the previous tumor bed, a focal hepatic lesion was found in segment VIII, suggestive of metastasis, along with ascites and radiological signs of