The case of a tender, isolated abdominal wall tumor within a Pfannenstiel incision due to a seeding deposit of endometrial tissue secondary to a previous obstetric operation (caesarean section) in a 39-year-old female without previously reported pelvic endometriosis is presented. The lesion clinically mimicked the appearance of an incarcerated incisional hernia at the outer corner of the healed Pfannenstiel incision. The preoperative differential diagnosis also included that of a locally forming post-operative tender granuloma and the remote possibility of an incisional endometrioma (although no link to menstruation could be made). Local malignancy was not taken as a serious possibility. Definitive diagnosis of the excised lesion was made at histology. The pre-operative diagnostic dilemma is presented, along with a short review of the literature.