426 Nasopharyngeal Malignant Melanoma Masquerading in the Gallbladder: The Importance of Histological Assessment

Introduction Metastatic malignant melanoma (MM) of the gallbladder (GB) is a rare entity which 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. Method A retrospective review of the electronic medical records of a 47-year-old patient who was diagnosed with metastatic MM of the GB was conducted. Data points included patient demographics, clinical features on presentation, radiological imaging, GB histology reports and outcomes was retrieved. Results This patient initially presented to our emergency department with a a protracted course of generalised abdominal. The patient was initially diagnosed with acute cholecystitis resulting in an emergency laparoscopic cholecystectomy. Following an emergency laparoscopic cholecystectomy, the histology incidentally revealed a melanoma with an unknown primary. Subsequently this was traced to the nasopharynx. Due to the presence of concurrent liver metastasis, systemic immunotherapy with palliative intent was commenced following a multi-disciplinary team discussion. Conclusions This case highlights the importance of sending all resected GB specimens following cholecystectomy for routine histological analysis. We argue against selectively choosing which specimens to send to histology based on radiological and/or intraoperative macroscopic inspection of resected tissue alone as this can delay or prevent the detection of sinister pathologies such as malignancy. We argue in favour of early detection in order to initiate early treatment to improve prognosis.