Rhabdoid Colorectal Carcinomas: Reports of Two Cases
A 62-year-old man was admitted to Konkuk University Medical Center due to occult blood in his stool. He had a six-year history of hypertension and cerebrovascular attacks. Colonoscopic examination revealed a huge mass in the sigmoid colon. Abdominal computed tomography (CT) revealed an ulcerofungating mass in the sigmoid colon and multiple enlarged pericolic lymph nodes. There was no evidence of distant metastasis on chest CT and positron emission tomography-computed tomography (PET-CT). The serum level of cancer antigen 19-9 (CA19-9) was within the normal range (15.75 U/mL). Low anterior resection was performed on a 4.5×4.0×1.2 cm sized ulcerofungating mass in the sigmoid colon (). Microscopically, most of the tumor was composed of sheets of large round and polygonal nuclei with vesicular chromatin along with abundant acidophilic cytoplasm which often contained hyaline-like inclusions. A poorly differentiated adenocarcinoma component was found in the peripheral portion of the tumor, located in the mucosa and submucosa, taking up 5% of the tumor. A transitional area from the poorly differentiated adenocarcinoma to the rhabdoid tumor was noted (). The tumor invaded into the pericolic adipose tissue and 10 out of 24 regional lymph nodes showed metastases. Adenocarcinoma cells were positive for mixed cytokeratin (CK), CK20, and epithelial membranous antigen (EMA), but focally positive for vimentin (). The rhabdoid tumor cells were positive for mixed CK, but focally positive for CK20 and EMA. In addition, the rhabdoid tumor cells were diffusely positive for vimentin, but negative for desmin (). E-Cadherin immunoreactivity was attenuated in the adenocarcinoma cells and negative in the rhabdoid tumor cells (). Immunohistochemical stains for MLH1, MSH2, MSH6, and PMS2 were positive in both types of tumor cells, while the stains for p53 were negative in both types of tumor cells. Immunohistochemical stains for smooth muscle actin (SMA), CD45, CD99, CD117, synaptophysin, neuron-specific enolase (NSE), and human melanoma black 45 (HMB45) were also negative in both types of tumor cells. The patient was treated with 12 cycles of adjuvant chemotherapy (FOLFOX: folinic acid, fluorouracil, oxaliplatin) and was alive without evidence of recurrence or distant metastasis for 36 months after surgery.