IV.6.1 Definition
Malignant neoplasm of melanocytes, represent- ing a subtype of melanoma which occurs on the mucosal epithelium of vulva and penis.
IV.6.2 Clinical Features
Melanoma of the vulva constitutes 2–4% of vul- va malignancies and accounts for 1–3% of all melanomas arising in women [9, 10]. It occurs most frequently in patients older than 60 years of age. Common locations are the labia majora and minora, but tumors may also arise on the clitoris or perineum. Clinically, the early stages are characterized by asymmetrical macules with tan-brown to black color variations and irregu- lar notched borders (Fig. IV.6.1a). Sometimes a multifocal origin is observed. More advanced
Chapter IV.6
Genital Melanoma
Ingrid H. Wolf IV.6
Contents
IV.6.1 Definition . . . .229
IV.6.2 Clinical Features . . . .229
IV.6.3 Dermoscopic Criteria . . . .230
IV.6.4 Relevant Clinical Differential Diagnosis . . . .230
IV.6.5 Histopathology . . . .230
IV.6.6 Management . . . .231
IV.6.7 Case Study . . . .231
References . . . .232
melanomas are characterized by deeply pig- mented plaques or ulcerated and bleeding pol- ypoid nodules (Fig. IV.6.2). Frequently, amela- notic tumors are recognized.
Male genital melanomas share their clinical (and histopathological) aspects with their fe- male counterpart. Melanomas occur most fre- quently on the glans penis, sometimes involving the urethral meatus [2].
Fig. IV.6.1. Melanoma in situ on the vulva. a Asymmet-
rical, sharply circumscribed black patches. b Increase in
number of atypical melanocytes as solitary units at the
dermo-epidermal junction and above it
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IV.6
Recently, distinct genetic differences (BRAF, NRAS) could be identified between non UV- light-associated mucosal melanomas and cuta- neous melanomas [1].
IV.6.3 Dermoscopic Criteria
Melanoma on genital regions show dermoscopi- cally polymorphous features with different col- ors from red to dark-brown and black. They usually present melanoma criteria, namely ir- regular streaks and globules, and inhomoge- neous pigmentation associated with an atypical vascular pattern. The pigment network may be prominent and irregular. An abrupt cut-off at the periphery, similar to melanomas in other lo- cations, is characteristic [4, 8].
An important indication for the use of der- moscopy in genital locations is to identify atypi- cal areas for biopsy and histopathology to dif- ferentiate melanoma from a benign pigmented proliferation.
IV.6.4 Relevant Clinical Differential Diagnosis
Vulvar/penile melanosis (melanotic macules) may be indistinguishable from melanoma in si- tu clinically. Also dermoscopically, melanomas can show overlapping features with vulvar mel- anosis. A typical parallel pattern with linearly arranged pigmentation (“fingerprint pattern”) or a “structureless pattern” can be found in mu- cosal melanosis but may sometimes also be present at the periphery of genital melanomas [6].
IV.6.5 Histopathology
Genital melanomas reveal the same characteris- tics as melanomas at other anatomic sites. They are broad lesions, poorly circumscribed, and asymmetric, and have atypical melanocytes ar- ranged as nests and single units at all levels of the epidermis (Fig. IV.6.1b). The growth pattern may be similar to acral melanomas. Demonstra- tion of melanocytes with thick dendrites, found also in the upper part of the epidermis, are a clue for the diagnosis of genital melanoma in si- tu. Invasive tumors reveal irregular nests and sheets with frequently spindle-shaped melano- cytes, looking like sarcomas. Lack of matura- tion and mitoses in the deeper dermal melano- cytic population are other important criteria [7]. Prognostic parameters include tumor thick- ness and ulceration.
A few cases of vulvar melanomas arising in a pre-existing vulvar nevus have been recorded in the literature.
Genital melanosis must be differentiated from vulvar and penile melanoma in situ. This is usually not so difficult because melanosis, in contrast to melanoma, reveals no percepti- ble – or only a slight – increase in the number of melanocytes which are situated as solitary units in the hyperpigmented basal layer. These mela- nocytes exhibit small and monomorphous nu- clei and delicate dendrites [5].
Fig. IV.6.2. Melanoma on the vulva with multifocal ap-
pearance
Genital Melanoma Chapter IV.6 231
IV.6.6 Management
The overall prognosis for genital melanomas is poor, with 5-year survival rates in the 30–50%
range. Local excision with adequate margins with or without sentinel node biopsy is the first- choice therapy [3, 9]. Radical surgery does not improve long-term survival time and should be performed only in larger tumors. For patients who refuse surgery, local radiotherapy is a rea- sonable option.
IV.6.7 Case Study
Patient Comment:
A 49-year-old woman presented with a 1.5- to 2-cm long-standing lesion in the genital area/
clitoris.
Question Asked By the Physician Which symptoms did you recognize?
Differential Diagnosis
The differential diagnosis was melanoma, mela- nosis, and melanocytic nevus.
Management
The management was surgical excision.
Fig. IV.6.3. Malignant melanoma on the vulva. a Asymmetrical poorly delineated patch with shades of dark brown, black, and gray. b Dermoscopy: irregular dots and globules, streaks, and bluish-white structures
a b
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