Small Intestinal Adenocarcinoma Involving a Submucosal Ectopic Lymph Node: A Case Report

An 83-year-old male with a 55-year history of Crohn's disease, ileocecectomy 40 years prior, and naturopathic treatment for 25 years, presented with nausea, vomiting, and abdominal pain. Computed tomography of abdomen and pelvis demonstrated partial small intestinal obstruction and a 4.4-cm solid left renal mass. After 3 months of recurrent intestinal obstruction and development of a pericolonic abscess, resection of the ileocolonic anastomosis, abscess, and partial nephrectomy were performed. Histopathology demonstrated chronic active enteritis with fistula tract formation, consistent with Crohn's disease, and moderately differentiated small intestinal adenocarcinoma extending from mucosa into subserosa. A submucosal intestinal lymph node-like structure containing adenocarcinoma demonstrated endothelial venules, open marginal and intermediate sinuses, multiple polarized germinal centers, and partial capsule, consistent with an ectopic lymph node, also called a tertiary lymphoid organ. Twenty mesenteric lymph nodes were negative for carcinoma. The renal mass was a papillary renal cell carcinoma, Stage I. Intestinal tertiary lymphoid organs form in chronic immune activation and have variable structures ranging from simple B and T cell clusters to organized groups with high endothelial venules and lymphatic vessels. Encapsulation of tertiary lymphoid organs is rare, with some sources claiming this entity is never encapsulated. To our knowledge, this is the first report of small intestinal adenocarcinoma involving a submucosal encapsulated tertiary lymphoid organ, the prognostic significance of which is uncertain. We suggest increased awareness of intestinal tertiary lymphoid organs as an entity and further studies to delineate the effect their involvement by adenocarcinoma imparts on survival.