Primary malignant melanoma of the urethra detected by urine cytology in a male patient

Abstract

Dear Editor:We read with interest the recent article by Hori et al. describing primary bladder melanoma diagnosed on voided urine cytology.1 Herein, we present a case of primary urethral melanoma diagnosed as suspicious for melanoma on voided urine cytology. To our knowledge, there have been rare case reports of primary bladder melanoma and one report of a primary urethral melanoma detected by urine cytology. 1-3 CaseThe patient was an 81-year-old man who presented to his urologist with benign prostatic hyperplasia and bladder outlet obstruction in the setting of a long history of lower urinary tract symptoms and hematuria for several months. Bladder outlet obstruction was demonstrated on urodynamics and attributed to an enlarged prostate. To evaluate for malignancy, voided urine was submitted and prepared as one Papanicolaou (Pap)-stained ThinPrepV R (TP) slide (Hologic, Boxborough, MA). Two prior voided urine specimens prepared similarly were negative for malignant cells over the prior 7 months. On microscopic examination, there were scattered large abnormal cells occurring singly and in small clusters (Figs. 1 and 2). The cells had enlarged nuclei, high nuclear-to-cytoplasmic (N/C) ratios, and prominent nucleoli. Several of the cells were bi-and multi-nucleate, and many contained dark-brown cytoplasmic pigment. The findings were suspicious for melanoma.A biopsy of the penile urethra performed 5 months later was diagnosed as melanoma (Fig. 3), confirmed by positive immunostaining for S100, HMB-45, and Melan-A, and negative pancytokeratin. A subsequent right axillary lymph node biopsy revealed metastatic melanoma.

Primary Malignant Melanoma of the Genitourinary System: A Systemic Review and Report of Eight Cases

“…The tumor may show epithelioid and spindle neoplastic cells in pure or mixed populations. Other rare cell types observed in urothelial melanomas include rhabdoid, clear, small cell, and giant cell morphologies [72,[75][76][77]. The tumor may rarely be mistaken for small cell carcinoma, lymphoma, and plasmacytoma.…”

“…Identification of melanoma cells in urine cytology, as well as melanuria or melanosis in the urine of patients with advanced metastatic melanoma, is an indication of the involvement of the genitourinary tract [71,72]. Therefore, awareness of cytomorphologic features of this entity should be considered to prevent misdiagnosis in urine cytology [73][74][75][76]. In urine cytology, melanotic-type GUMM exhibits large single cells or small clusters of malignantappearing cells with intracytoplasmic melanin pigments.…”

“…Bi-nucleation, multi-nucleation, and occasional intranuclear inclusions are other observed features. Differential diagnoses of melanotic melanomas include pigments such as hemosiderin, lipofuscin, and melanosis [75][76][77][78][79][80][81]. Hemosiderin pigments presenting in histiocytes, and melanosis, defined as the deposition of melanin pigments in urothelial cells theoretically, are accompanied by benign nuclear features of their host cells.…”

“…Prostatic adenocarcinoma seldom is detected in urine cytology as cells with prominent nucleoli are usually arranged in cohesive clusters or acini. Lastly, metastatic tumors sometimes have specific features such as intracytoplasmic mucinous vacuoles in signet ring cell carcinoma of the stomach or linear arrangement of cells of metastatic lobular breast carcinoma that make them distinguishable from melanoma cells [75,76,82]. In these situations, the presence of accurate clinical information about other malignancies is vital.…”

Primary malignant melanoma of the male urethra: a case report

“…Primary malignant melanomas of the genitourinary tract are rare, representing <1% of all melanomas and accounting for ~4% of urethral carcinomas ( 1 ). Primary urethral melanoma is three times more common in women than men ( 2 ) and tends to occur in older patients, averaging 65 years of age ( 3 ).…”