Rectal tonsils are localized hyperplastic lymphoid tissues in the rectum, and the initial endoscopic findings are consistent with those for neoplastic lesions. However, rectal tonsils are benign entities, and the diagnosis should be made cautiously. A 70‐year‐old man presented with pain on defecation with rectal bleeding. Colonoscopy revealed a 3‐cm protruding mass in the rectum with mucosal erosion, but no malignant features were observed on forceps biopsy. Endoscopic ultrasonography (EUS) showed that the lesion was a hypoechoic mass without blood flow. Fine needle aspiration under EUS revealed no malignant components, although the size of the lesion had shrunk, and symptoms, such as blood‐stained stool, tenesmus, and discomfort during defecation, had resolved. A second forceps biopsy showed intermediate‐sized lymphocytes without lymphoepithelial lesions. Based on immunostaining, the lesion was diagnosed as a rectal tonsil.

Rectal tonsils occur due to localized proliferation of reactive lymphoid follicles in the submucosa or muscularis mucosa. However, endoscopic diagnosis is difficult since less invasive treatment is performed for neoplastic lesions of the rectum to preserve the function of the anal sphincter. Diagnosis and treatment of small lesions might be possible by endoscopic resection; however, for relatively large lesions, formulating a diagnosis based only on biopsy specimens becomes even more difficult. Therefore, repeated biopsies might be helpful for the diagnosis of rectal tonsils and for excluding other neoplasms.

• colonoscopy
• lymphoid tissue
• polyp
• rectum
• submucosa

• Colitis
• Lymphoid hyperplasia
• Mucosa-associated lymphoid tissue lymphoma
• Rectum
• ulcerative

• Endoscopic procedure
• Histopathology
• Lymphoid hyperplasia
• Rectal neoplasia
• Submucosal tumor

The rectal tonsil, a reactive proliferation of lymphoid tissue located in the rectum, is rare. Histologically, benign lymphoid hyperplasia of the rectum is usually characterized by large lymphoid follicles with active germinal centers and a narrow surrounding mantle zone and marginal zone. This lesion is benign, but must be differentiated from the polypoid type of mucosa-associated lymphoid tissue lymphomas. In the current paper, we present a case of rectal tonsil in a 59-year-old woman. We describe the endoscopic ultrasound imaging findings with literature review.

• Rectum
• Tonsil
• Lymphoid hyperplasia
• Rectal tonsil
• Lymphoid follicles

• Biomarkers/analysis
• Biopsy
• Colonoscopy
• Diagnosis, Differential
• Endosonography
• Female
• Humans
• Hyperplasia
• Immunohistochemistry
• Lymphoid Tissue/chemistry
• Lymphoid Tissue/pathology
• Lymphoid Tissue/surgery
• Lymphoproliferative Disorders/diagnosis
• Lymphoproliferative Disorders/metabolism
• Lymphoproliferative Disorders/pathology
• Lymphoproliferative Disorders/surgery
• Middle Aged
• Predictive Value of Tests
• Rectal Diseases/diagnosis
• Rectal Diseases/metabolism
• Rectal Diseases/pathology
• Rectal Diseases/surgery