P27.09: The importance of keeping an open mind

Adnexal masses are found in females of all ages and are most frequently of gynecological origin. Ultrasonography is usually the first line investigation and often sufficient to determine the origin of the mass, and its nature. Solid adnexal masses can present a diagnostic dilemma, particularly if the ovaries are not clearly seen as separate structures, a situation often encountered in postmenopausal women. In this group MRI can be useful as a problem-solving technique. In this case report we present an 80 year old lady with 4 month history of weight loss, a change in bowel habit and lower abdominal pain. As part of her diagnostic work-up an ultrasound scan demonstrated a 9cm solid adnexal mass, separated from the uterus which was noted to contain small intramural fibroids. Neither ovary was identified. The differential diagnosis was felt to be of a primary or secondary ovarian tumor or a pedunculated subserosal fibroid. Pelvic MRI was performed for further characterisation and this confirmed a well-defined presacral solid mass towards the left of midline. The lesion was clearly separate from the uterus and the demonstration of a normal postmenopausal right ovary lead to the possible diagnosis of a left ovarian tumor. Following surgical excision the final diagnosis of pararectal Schwannoma was confirmed on histophathological and immunohistochemical testing. Schwannomas of the colon and rectum are rare benign non-epithelial tumors originating in the Schwann cells, only a small number of cases being reported in the world literature. This case report demonstrates the importance of considering extra-gynecological causes of female pelvic masses, in this instance a rectal Schwannoma. Diagnostic clues include the history of altered bowel habit (on closer enquiry, difficulty with defecation), and the presacral/pararectal location.