Malignant melanoma of the gall bladder is rare. Most cases are metastatic and primary gall bladder melanoma is even more rare. We report a case of primary malignant melanoma of the gall bladder which illustrates the diagnostic challenge posed by this condition. Histopathology and immunohistochemistry play a pivotal role in making a diagnosis and ruling out conditions which mimic it such as xanthogranulomatous cholecystitis and other relatively common epithelial malignancies. We tested for prognostic and predictive markers including BRAF and PD-L1 and immunohistochemistry showed positive staining for BRAF. The tumour cells expressed HMB-45 and were negative for cytokeratin and CD68, favouring a diagnosis of malignant melanoma and excluding the possibility of xanthogranulomatous cholecystitis and carcinoma. On follow-up at 3 months there was no evidence of recurrence of metastasis.
- Gastrointestinal surgery
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Contributors KK, AZ, AC and NH were responsible for drafting the text, sourcing and editing the clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content. NH and AC gave final approval of the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.