Intestinal non-Hodgkin lymphoma with peritoneal lymphomatosis mimicking acute appendicitis.

The gastrointestinal tract is the most frequent extranodal site of non-Hodgkin lymphoma (NHL), accounting for up to 40% of cases. However, appendiceal lymphoma is exceptionally rare, with peritoneal involvement being even rarer. Appendiceal lymphoma often mimics acute appendicitis (AA), although it is an uncommon initial manifestation of intestinal NHL, complicating diagnosis. We report a 29-year-old male with human immunodeficiency virus (HIV) who presented with AA. An open appendectomy was planned; however, intraoperative findings- including cecal induration, ascites, peritoneal thickening, and macronodular lesions on the peritoneum and intestines-led to abandonment of the procedure. Postoperative evaluation excluded peritoneal tuberculosis (PTB), while computed tomography (CT) suggested peritoneal carcinomatosis (PC). Histopathological analysis of a parietal peritoneum specimen provided the definitive diagnosis of NHL. Appendiceal NHL should be considered in HIV-positive patients with AA. Routine histopathological evaluation and surgical intervention are essential for accurate diagnosis and effective management.