A Case of Primary Cutaneous Endometriosis on the Umbilicus

초록

Endometriosis is defined as the presence of endometrial tissue outside the uterine cavity, and causes chronic pain associated with the menstrual cycle1. It occurs mainly in the ovaries but can also affect extra-peritoneal tissues, such as the vagina, cervix, lungs, and surgical wound sites2. Cutaneous endometriosis represents less than 1% of all ectopic endometrium and is classified into primary and secondary categories3. Primary cutaneous endometriosis is very rare and not associated with surgical procedures; however, secondary cutaneous endometriosis occurs on abdominal and pelvic scars from gynecologic surgery including hysterectomy, episiotomy, cesarean section, and laparoscopy3. The pathogenesis of primary endometriosis remains unclear, but secondary endometriosis is caused by iatrogenic implantation of endometrial cells during surgical procedures3. Cutaneous endometriosis is uncommon and can be misdiagnosed as keloid or dermatofibroma, because the clinical presentation is similar. A 39-year-old woman presented with a painful, solitary, protruding mass on the umbilicus for 1 year. Its size gradually increased, and pain and bleeding had been worsened according to her menstrual cycle. She never had surgery on her umbilical area. Before visiting our clinic, she visited the gynecology and general surgery outpatient department, and imaging studies including ultrasound were performed, but there were no specific findings. On physical examination, a firm, multi-lobulated, solitary tender mass was noted on the umbilicus that was heterogeneous in color (Fig. 1). A punch biopsy was performed for differential diagnosis of keloid, hypertrophic scar, and cutaneous endometriosis. Histopathologic examination showed multiple dilated glandular structures in the dermis. They were surrounded by endometrial-type stroma and perivascular infiltration of lymphocytes. Endometrial glands are lined by tall columnar epithelium with features of decapitation secretion (Fig. 2). Based on these findings, the patient was diagnosed with cutaneous endometriosis. After diagnosis, she was transferred to the gynecology department. Since she wanted to treat with non-surgical method, she is being treated with dienogest, which inhibits trophic effects on the endometrium by reducing estradiol production. In our case, although the patient had a history of cesarean section, she was diagnosed with primary cutaneous endometriosis because the lesion did not occur at the surgical site. Primary umbilical endometriosis is initially rare condition, however, reported cases have been increasing. Therefore, adequate differential diagnosis including keloid, and metastasis of visceral cancer is crucial4. In this case, although not performed, staining for estrogen receptor (ER), progesterone receptor (PgR), and CD10 could have provided valuable insights into the diagnosis of endometriosis. Notably, according to previous studies, CD10 staining is deemed as useful as ER or PgR in elucidating the presence of endometriosis. Furthermore, CD10 proves valuable for conclusively diagnosing this condition, as it exhibits positivity in the interstitium of cutaneous endometriosis, even when the presence of glandular cavities is not distinctly evident5. Several possible mechanisms for the pathogenesis primary endometriosis have been suggested such as lymphatic or vascular migration, cellular metaplasia, and iatrogenic metastasis3. Further studies are needed to investigate the exact mechanism of primary extra-pelvic endometriosis, including cutaneous endometriosis. Herein, we report an interesting case of primary cutaneous endometriosis on the umbilicus.

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