Amelanotic melanoma is a rare malignancy and the prognosis is usually poorer than that of pigmented melanomas, because of delay in establishing the correct diagnosis, and in treatment initiation. In our case report, we present a the Flurodeoxyglocose Positron Emission Tomography-Computed Tomography (FDG PET/CT) findings of a patient suffering from malignant amelanotic melanoma and its histopathological confirmation and immunohistochemistry (IHC) correlation In the described case, amelanotic melanoma masqueraded as adenocarcinoma of the rectum in the pathology as well the clinical course. Our case highlights the importance of obtaining a tissue diagnosis and IHC confirmation whenever unusual PET/CT findings are encountered.