To the Editor
A rectal mucosal melanoma is a rare but highly malignant neoplasm affecting females more often than males. Most of them are located in the distal rectum and appear as a polypoid or fungating intraluminal mass. The disease has aggressive biological behavior and is usually advanced at presentation. The prognosis is poor due to early metastases and being refractory to therapeutic modalities Citation[1–3].
A 40 year old female with anal bleeding mimicking a hemorrhoid was found to have a tumor in the rectum by digital examination. A diagnosis of a malignant melanoma was made after a tissue biopsy (). 18F-fluoro-deoxyglucose (FDG) PET for initial staging demonstrated focally increased uptake in the rectum and bilateral inguinal lymph nodes (A, B). In addition, there was nodular uptake in the posterior left upper thorax (C), consistent with a hot spot seen on the MDP bone scan (D), which was considered to be a metastatic rib lesion.
FDG-PET accompanied by sentinel node biopsy is a novel modality for the staging and restaging of cutaneous malignant melanomas Citation[4–7]. A few cases regarding its utility in mucosal malignant melanomas have been reported in the literature. To our knowledge, this is the first report of a case of a malignant melanoma arising from the rectum with FDG uptake Citation[8–10]. Although a lesion with infectious process may present with enhanced glucose metabolism and increase FDG uptake, a previous report concerning human papilloma virus which could often be isolated from ano/rectal mucosa as an etiological factor for emerging malignant melanoma in sun sheltered areas, was not identified Citation[11].
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