Metastatic Melanoma to the Rectum: A Case Report: 1522

We present the case of an 85 year-old female with a history of cutaneous melanoma status post excision, who presented to the emergency room with painless bright red blood per rectum for one day. She was hemodynamically stable upon presentation and her physical examination was essentially unremarkable. Routine labs including CBC were within normal limits. A colonoscopy was performed, which demonstrated a friable rectal mass, measuring 4 cm in size, just proximal to the dentate line. Biopsies of the mass were obtained and pathology was consistent with malignant melanoma. CT chest, abdomen and pelvis was negative for metastases. An MRI was performed and demonstrated the rectal mass abutting the internal anal sphincter and extending through the muscularis propria along the right border without regional adenopathy or evidence of extension to adjacent organs. The patient's case was discussed at Tumor Board and a PET-CT scan was recommended in addition to testing for B-RAF and KIT. PET CT was negative for metastatic disease. Molecular testing was positive for KIT but negative for B-RAF. Surgery was not performed, given concern for poor healing and low likelihood of impacting prognosis. Chemotherapy was initiated with a regimen of ipilimumab and nivolumab as recommended by Oncology. She is currently undergoing her 4th cycle of chemotherapy, which she is tolerating fairly well. She is due for follow-up imaging this month. Rectal malignant melanoma is a rare and aggressive cancer. It predominantly occurs in women in their 7th and 8th decade. It usually presents with rectal bleeding and tenesmus. S-100 stain on biopsy is strongly suggestive of the diagnosis. Surgical therapy is generally controversial given lack of evidence for improved survival and is generally individualized according to severity of symptoms, presence of metastatic disease, and overall health and functional status of the patient. Most treatment regimens are extrapolated from cutaneous melanoma studies and incorporate combinations of chemotherapy, immunotherapy and radiotherapy. Prognosis is generally poor regardless of treatment and median survival is about 20 months.FigureFigure