A 35 year old female was referred to the pelvic pain clinic at the Royal London Hospital with a six-month history of a tender superficial mass below the umbilicus, intermittent pelvic pain and dysmenorrhoea. There was no reported dyspareunia or dyschezia. She reported increased urinary frequency over this time period. She had two previous emergency Caesarean sections in 2000 and 2004. She worked as a cleaner and reported that her symptoms were interfering with her work. There was no other medical history of note. Following clinical examination, an MRI of the pelvis was carried out. The MRI scan revealed that the ovaries and sigmoid colon were adherent to the posterior myometrium, and the uterus was anteverted and adenomyotic. A spiculated subcutaneous soft tissue lesion was identified just inferior to the umbilicus, extending from the abdominal wall superficial fascia just into rectus abdominus, measuring 4.4 cm × 2 cm (Figure 1). A biopsy taken the previous week showed the lesion to be consistent with endometriosis. The patient was listed for surgery.

Figure 1: The lesion to be consistent with endometriosis.

Palmer’s point laparoscopy and pelvic adhesiolysis was carried out. An abdominal skin incision was made and the umbilical wall endometrioma was excised (Figure 2) under general anaesthesia.

Figure 2: The umbilical wall endometrioma.

Endometriosis is described as a common disorder involving migration of uterine endometrium outside of the uterus. It is a wellrecognised cause of infertility and pelvic pain, as a result of adhesions and distorted anatomy. Endometriosis is dependent upon oestrogen [1]. Abdominal wall endometrioma is a focus of endometriosis presenting as a tender mass. The incidence of endometrioma within the surgical scar post-Caesarean section has been reported as between 1 and 2% Abdominal wall endometriosis is thought to be caused by accidental transfer and implantation of endometrial cells into the surgical site during a surgical procedure, such as a Pfannenstiel incision for a Caesarean section. These deposited cells are then stimulated by estrogen to form foci of endometriosis [2]. Mistrangelo et al. [3] carried out a retrospective observational cohort study of five patients with Caesarean surgical scar endometriosis. The mean age of the patients in the cohort was 38.6 years. All of the patients reported experiencing abdominal pain and an associated mass. The treatment in all patients was a wide margin surgical excision, and direct closure of the surgical wound. Recurrence occurred in one patient after 12 months and was managed surgically. From the above study, it can be reasonably concluded that abdominal scar endometrioma presents as a tender mass, which can be managed via surgical excision with a wide margin to avoid recurrence.

This case highlights a rare differential diagnosis for an anterior abdominal wall mass, and the importance of thorough gynaecological history taking and examination.