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Penis and scrotum
Other malignancies
Melanoma
Editor: Antonio Cubilla, M.D. and Alcides Chaux, M.D. (see Author/Reviewers page)
Revised: 25 May 2010, last major update May 2010
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.
Definition
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● Relatively rare tumor of penis, similar to counterparts elsewhere
● ICD-O: 8720/3
Epidemiology
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● White men ages 50-70 years
Sites
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● Preferential location is glans (60-80%) followed by shaft and foreskin
● Distal urethra location is exceedingly uncommon and tends to affect the fossa navicularis
Etiology
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● Risk factors include preexisting nevi, ultraviolet radiation and history of melanomas elsewhere
Clinical features
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● Most common tumor in penis after squamous cell carcinoma, but accounts for < 1% of all penile malignant tumors
● Small, brown to black lesions similar to melanomas elsewhere
● Ulceration is common
● Distal urethra melanomas are typically polypoid
● 50% have inguinal nodal metastases at diagnosis
Poor prognostic factors
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● Presence of ulceration, tumor depth >3.5 mm, tumor size (diameter) >15 mm, nodal or distant metastases (Urology 2007;70:143)
Case reports
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● 64 year old with melanoma in situ of glans (Eur J Dermatol 2005;15:113)
Treatment
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● Partial penectomy or wide local excision (J Urol 2005;173:1958)
● Close follow up for recurrence (Urology 2008;72:1185)
Clinical images
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Ulcerated dark mass involves the Melanoma in situ
prepuce and coronal sulcus
Gross description (Macroscopy)
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● Flat dark macula, ulcer or black / blue / red nodule with irregular edges
Micro description (Histopathology)
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● Radial and vertical growth phases similar to melanoma elsewhere
● Variegated growth patterns are solid, nested, fusiform or mixed
● Polygonal neoplastic cells with abundant eosinophilic cytoplasm and marked nuclear atypia
● Coarse brown intracytoplasmic pigment in most cases
● Abundant and atypical mitoses
● Clear, vacuolated, rhabdoid or pleomorphic cells in some cases
● Preexisting or coexisting melanosis, melanotic nevi (J Cutan Pathol 2009;36:444) or lentiginous melanosis is occasionally found
Micro images
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Deeply invasive nodular tumor of glans Melanoma in situ
Other images: glans; glans with urethral involvement #1; #2
Positive stains
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● HMB45, MelanA, S100
Differential Diagnosis
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● Benign melanocytic neoplasia: maturation present; no nuclear pleomorphism, no pagetoid spread
● Paget’s disease: very difficult to distinguish from melanoma morphologically in radial growth phase; positive for MUC-1, MUC-5AC, CAM 5.2, EMA, CEA and GCDFP-15; negative for melanocytic markers
● Sarcomatoid carcinoma: nests of squamous cells within the tumor, PeIN present, no melanin in tumor cells, positive for pan-cytokeratin, CK 34-beta-E12 and p63; negative for melanocytic markers
● Penile primary sarcoma: no intraepithelial component, no melanin in tumor cells; negative for melanocytic markers
End of Penis and scrotum > Other malignancies > Melanoma
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