直腸に発生した良性リンパ濾胞性ポリープ（別名rectal tonsil）の1例

Benign Lymphoid Polyp in the Rectum (Rectal Tonsil), Report of a Case

　直腸および肛門管の良性リンパ濾胞性ポリープは正常のリンパ濾胞に由来する限局性の増殖，すなわちlymphoid hyperplasiaであり，大腸・肛門の腫瘍および腫瘍様病変の病理組織学的分類では非上皮性の腫瘍性病変に属する疾患である．別名rectal tonsil，benign lymphoma，lymphoid polyp，lymphoadenoma，benign giant follicular lymphomaとも呼ばれ，1890年Shattockにより初めて記載された．まれな疾患で臨床診断はしばしば困難であり，また組織像はときにはリンパ肉腫，giant follicular lymphomaと誤ることがある．

　A benign lymphoid polyp in the rectum is localized proliferation of submucosal normal lymphoid derived from chronic inflammatory stimulation, which is also called as lymphoid hyperplasia, and is a rare disease first reported by Shattock in 1890.

　Patient: A 62-year-old woman.

　Chief complaint: Rectal bleeding.

　Barium enema examination: The filling picture in the prone position revealed a poor-stretching part about 30mm long at the Rb. It area; the reversed oblique picture in the prone position showed a 45×32mm smooth-surfaced and homogeneous projected defect at the same area; the re-standing picture showed a bridging-fold like a defect near the anus; and the compression picture showed a swelling defect, measuring about 43×35mm, and an irregular spot, measuring 12×7mm, suggesting erosion in it.

　Romanoscopic examination: A grayish brown mass of a thumb-head size was seen in the Rb, It area 5cm apart from the anus; it was smooth-surfaced, polyp-like and pedunculated.

　Biopsy: The mucosa was slightly atrophied; the stroma showed infiltration by cells mainly consisting of lymphocytes; numerous masses of lymphoid cells suggesting follicle were found partially but any true neoplasm was ruled out.

　She was temporarily diagnosed as having a nonepithelial benign tumor clinically, and the mass was removed.

　Examinations of the resected sample: It was a 45×35×20mm short-pedicled, almost sessile mass: it was grayish brown and had various erosions on the surface. Histologically, it was a follicular phyma swelling in the submucosal layer; it invaded into the mucosal muscular layer and showed erosions due to peeling of the superficial epithelium. The follicle had an obscure boundary and the reaction center was slightly recognized. The cell proliferation in the boundary was mainly composed of matured lymphocytes and juvenile one: many plasma cells were also present there. Silver fibers were not seen in any part of the proliferated cells; the infiltration into the muscular layer was partially seen. The lesion was thus diagnosed as benign lymphoid polyp.