Background: The development of a mass in association with a previous surgical scar can pose a diagnostic dilemma due to similarities in appearance to hernias, abscesses, hematomas, or desmoid tumors. Scar endometriosis is an uncommon cause of such a lump, but malignant change within this ectopic tissue is exceptionally rare.
Case: We present a case of a 55-year-old woman who was found to have an isolated clear cell adenocarcinoma in an area of scar endometriosis more than 30 years after an open tubal sterilization. This mass was initially thought to be an incisional hernia, but was later diagnosed intraoperatively by frozen section and then incompletely excised, highlighting the difficulties in preoperative diagnosis as well as surgical treatment.
Conclusion: Malignant change within scar endometriosis is rare, but increased awareness of this phenomenon is required. Vigilance is paramount and a mass located in or close to a surgical scar should be treated with suspicion.