Since Cullen first described inguinal endometrioma, there have been several cases reported in the literature. This lesion is of general surgical interest, for the preoperative diagnosis has usually been incarcerated inguinal hernia, whether or not a hernia sac was actually present. The aspect of the subject which has gained most attention, however, is the search for an explanation of the pathogenesis.
Sampson mentioned five possible theories which could account for the presence of endometrium in the region of the external inguinal ring: 1. Muellerian tissue might be placed beside the round ligament as a result of faulty embryonic development. 2. Mesothelium in the region of the round ligament might undergo metaplasia. 3. Pelvic endometriosis could reach the groin by direct growth extension. 4. Endometrial metastasis could take place by way of the blood or lymph vessels. 5. If a hernia sac were present, an endometrial implant could reach the groin
PATTERSON DC, GEER WA, STRAYER EM. A CASE OF INGUINAL ENDOMETRIOMA. Arch Surg. 1941;42(3):577-580. doi:10.1001/archsurg.1941.01210090126011