A Case of Rectal Carcinoma Complicated with Adult T-cell Leukemia/Lymphoma Diagnosed by an Inguinal Lymph Node Biopsy

Background: Recently, double cancer is no longer uncommon. It is Particularly difficult to determine whether swollen lymph nodes (LNs) indicate malignant lymphoma or metastasis of other carcinoma. We experienced a case of rectal carcinoma complicated with adult T-cell leukemia/lymphoma (ATLL). Case presentation: We encountered a 77-year-old woman who had visited a previous hospital due to bloody stool. Colonoscopy revealed a 10-cm tumor in the lower rectum. Given its pit pattern and surface and vessel pattern, she was suspected of having adenocarcinoma in situ. However, enhanced computed tomography (CT) showed LN swelling around the rectum, and her bilateral inguinal LNs were palpable. Colonoscopy and a biopsy performed at our hospital showed adenoma (Group 3) with no malignant findings. We performed an inguinal LN biopsy and diagnosed her with ATLL. We suspected the rectal mass either be rectal carcinoma or ATLL invasion. We performed chemotherapy for ATLL. The inguinal LNs became no longer palpable, but the rectal mass did not shrink, so we performed operative resection for diagnostic treatment. Thereafter, we diagnosed her with double cancer of rectal adenocarcinoma and ATLL. Conclusion: It is difficult to determine whether swollen LNs indicate malignant lymphoma or metastasis of other carcinoma without performing an LN biopsy. However, a diagnosis of metastasis or non-metastasis does not influence either the staging of the carcinoma or the treatment plan.