Case Report
Copyright ©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Aug 26, 2023; 11(24): 5721-5728
Published online Aug 26, 2023. doi: 10.12998/wjcc.v11.i24.5721
Malignant melanoma of the prostate: Primary or metastasis? A case report
Hong Zhao, Chun Liu, Bin Li, Jian-Ming Guo
Hong Zhao, Department of Urology, Shanghai Xu-Hui Central Hospital, Shanghai 200001, China
Chun Liu, Department of Radiology, Shanghai Xu-Hui Central Hospital, Shanghai 200001, China
Bin Li, Department of Pathology, Shanghai Xu-Hui Central Hospital, Shanghai 200001, China
Jian-Ming Guo, Department of Urology, Zhongshan Hospital, Fudan University, Shanghai 200001, China
Author contributions: Zhao H contributed to study protocol and manuscript writing; Liu C contributed to the manuscript writing; Li B contributed to data collection; Guo JM contributed to project development; Zhao H and Liu C contributed equally to this work; All authors have read and approved the final version to be submitted.
Informed consent statement: The patient has provided informed consent.
Conflict-of-interest statement: The authors declare that there are no financial and personal relationships with other people or organizations that could inappropriately influence our work. There is no professional or other personal interest of any nature in any product, service and/or company that could be construed as influencing the position presented in, or the review of this manuscript.
CARE Checklist (2016) statement: The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Jian-Ming Guo, MD, PhD, Academic Editor, Doctor, Department of Urology, Zhongshan Hospital, Fudan University, No. 180 Fenglin Road, Shanghai 200001, China. drguojm@126.com
Received: April 5, 2023
Peer-review started: April 5, 2023
First decision: May 15, 2023
Revised: May 24, 2023
Accepted: August 3, 2023
Article in press: August 3, 2023
Published online: August 26, 2023
Abstract
BACKGROUND

Malignant melanoma of the prostate is rare. Twenty-five studies describing 45 cases have been reported. Prostate melanoma is characterized by an insidious onset and poor prognosis. The prognosis and treatment vary according to primary or secondary melanoma.

CASE SUMMARY

A 75-year-old man attended the hospital due to low back pain of 2 mo duration. He denied a history of trauma or abnormal urinary symptoms. Digital rectal examination showed indentation in the left lobe of the prostate, 1 cm in diameter. His prostate-specific antigen was 5.6 ng/mL and 18F-fluorodeoxyglucose positron emission tomography computed tomography (18F-FDG-PET/CT) showed focal glucose metabolism in the left lobe. Imaging showed bone metastases to T12 and bilateral ribs. Transperineal prostate biopsy was done and three tissue specimens on the left side showed prostate adenocarcinoma (Gleason score 3 + 3 = 6), but the specimen on the right side showed malignant melanoma. The patient underwent T12 tumor resection and pathology findings indicated metastatic malignant melanoma. The patient underwent gastroscopy and colonoscopy, and gastroscopy revealed multiple mucosal black spots in the gastric body and fundus. The patient was diagnosed with secondary malignant prostate melanoma and primary gastric disease.

CONCLUSION

Diagnosis of primary prostate melanoma requires caution and 18F-FDG-PET/CT may result in false-negative detection of melanoma.

Keywords: Melanoma, Prostate, Primary, Metastases, Diagnosis, Case report

Core Tip: Malignant melanoma of the prostate is rare. To date, 25 studies describing 45 cases have been reported. There is a significant difference in prognosis between primary and secondary cases. We report a case of secondary malignant prostate melanoma with primary gastric disease. We also review the literature on 10 cases of primary prostate melanoma, and found that most cases did not receive sufficient tests and 18F-fluorodeoxyglucose positron emission tomography computed tomography (18F-FDG-PET/CT) was false-negative. We conclude that caution should be used in the diagnosis of primary prostate melanoma, and 18F-FDG-PET/CT may result in false-negative detection of melanoma.