Primary versus secondary cutaneous endometriosis: Literature review and case study

Cutaneous endometriosis, characterized by the presence of endometrium or endometrial-like tissue outside of the uterine cavity, is an uncommon and chronic disease. Depending on a patient's history, cutaneous endometriosis is classified as either primary cutaneous endometriosis (PCE) or secondary cutaneous endometriosis (SCE). We report a case of SCE presenting with the classic triad of previous caesarean section, subcutaneous nodules at the site of the scar, and pain associated with menstruation. Considering histopathology as the standard, we confirmed a diagnosis of cutaneous endometriosis by ultrasound and histopathology. Furthermore, we compared and analyzed the clinical characteristics of PCE and SCE, the study included 20 and 14 patients with cutaneous endometriosis diagnosed with PCE and SCE respectively. In the PCE group, the mean age of patients at the onset was 33.7 years, while it was 40.6 years in the SCE group. The mean disease-duration time of PCE was shorter than that of SCE (1.3 vs. 2.8 years, P > 0.05). The most common clinical presentation of PCE and SCE was a nodule (90% vs. 86%). The PCE was mainly bleeding with pain (45%), whereas the SCE of only pain and bleeding with pain accounted for the same proportion (45%). The most common sites of PCE and SCE were in the umbilical region (90% vs. 57%, P < 0.05). In our study, some statistically significant difference was found between different types of CE and it may contribute to improve clinicians' understanding of the disease, and perform early diagnosis and treatment.