A Case of Anal Malignant Lymphoma in which Excisional Biopsy was Useful for Confirming the Diagnosis

Abstract

An 85-year-old man presented with a painful anal tumor and was referred to our hospital for further examination. Anal canal cancer was suspected on CT, but tumor markers were not increased. Endoscopic biopsy was performed, but epithelial cells could not be identified, and the tissue was severely crushed, so no definitive diagnosis was made. To relieve the anal pain and to make a definitive diagnosis, a colostomy and an excisional biopsy were performed. Pathological findings showed that the epithelium had disappeared, large lymphocyte-like cells were diffusely proliferated, and B cell lineage markers such as CD20 were positive. A definitive diagnosis of diffuse large B cell lymphoma of the anal canal was made. Chemotherapy was performed, and a complete response was obtained on CT evaluation 2 courses later. For gastrointestinal malignant lymphoma, chemotherapy is the first choice in principle. Lymphoma tissues are relatively soft, and the epithelium may disappear. Thus, excisional biopsy is thought to be useful if a definitive diagnosis cannot be made by endoscopic biopsy.