AB180. Caught off guard—a case study of rare pathology “malignant melanoma”

Background: Malignant melanoma is an uncommon cause of gastrointestinal tract metastasis, despites views to the contrary. It’s presentation frequently differs from other causes of colonic cancers as patients are generally well preceding the event are often not anticipated. Most often, they are diagnosed during an autopsy. Only 0.2% to 9% of all malignant melanoma will have gastro intestinal gastrointestinal (GI) tract involvement. This case report describes a 49-year-old lady, diagnosed with this rare pathology.

Methods: A 49-year-old female presented to Emergency Department with 12-hour history of intermittent right upper quadrant right upper quadrant (RUQ) pain, associated with nausea. Patient had laparoscopic cholecystectomy 1 month prior to this presentation due to symptomatic gallstones (pre op ultrasound showed gallstones in gallbladder, with normal common bile duct common bile duct (Cbd) and liver/pancreas). Her other past medical history includes epilepsy, anxiety/depression disorder and benign mole excised 5 years ago. Patient was vitally stable on presentation. On examination her abdomen was mild tender at RUQ area, and rest of the examination was normal. Her infection (white blood cells 6.3) and inflammatory markers (C reactive proteins were 6) were normal. Apart her Bilirubin of 6 rest of the liver function tests were high. She was admitted under surgical team for further investigation. Her most common pathology was CBD obstruction. Surprisingly, her ultrasound showed innumerable target like lesions within liver. Both of the ultrasound images were re-compared, and shockingly, liver was normal in her last presentation. Urgent computer tomography of thorax abdomen and pelvis (CT TAP) showed multiple metastasis in lung and liver, with unknown primary source. Upper gastroscopy revealed multiple melanocytic lesions in gastric region. Colonoscopy however was normal.

Results: Biopsies results of liver and Gastric lesions revealed Melan A, hence confirming malignant melanoma. Case was discussed in multiple disciplinary team (MDT), and she was opted for immunotherapy.

Conclusions: Malignant melanoma is malignant tumour of melanocytes. It’s present mostly in skin, eyes, meninges and gastro intestinal tract (GIT) mucosa. Malignant Melanoma accounts for 1–3% of all the tumours. Histopathological features consist with positive Melan A, S100 and HMB-45. Only 0.2–9% of all the patients with malignant melanoma will have GI tract involvement, out of which the most frequent site will be the small bowel, up to 58%, followed by large bowel of about 22%. About 20–40% GI tract malignant melanoma involves stomach, but often diagnosed during post mortem. Oesophageal being the most uncommon site, accounts for 0.1–0.2% of all the GI tract melanomas. Due to their aggressive metastatic behaviour, mostly they are diagnosed ante-mortem. Overall global prognosis is 7–22 months. Palliation can be achieved with surgical resection.

Keywords: Malignant melanoma; gastro intestinal tract (GIT)