Nasopharyngeal malignant melanoma masquerading in the gallbladder: the importance of histological assessment

Metastatic melanoma of the gallbladder is a rare entity that is often diagnosed late, leading to a poor prognosis. The disease may present insidiously as acute cholecystitis or remain asymptomatic. Optimal management remains unclear but surgical resection is considered the mainstay of treatment for this condition. We report the case of a 47-year-old man who suffered a protracted course of generalised abdominal symptoms eventually culminating in a diagnosis of acute cholecystitis. Following an emergency laparoscopic cholecystectomy, the histology revealed a melanoma with an unknown primary. Subsequently this was traced to the nasopharynx. Because of the presence of concurrent liver metastasis, systemic immunotherapy with palliative intent was commenced following a multidisciplinary team discussion. This case highlights the importance of sending clinical specimens for histological analysis. We argue against selectively choosing which specimens to send for histology because radiological and/or intraoperative macroscopic inspection of resected tissue alone can result in a missed diagnosis.