In this report, we experienced a rare kissing nevus of the penis. Kissing nevi are two adjacent brownish to black pigmented lesions that split along with division of the body during embryogenesis. Kissing nevi of the eyelids were first described by Von Micheal in 1908, and the name was first used by Fuchs13
in 1919. Since then, at least 45 additional cases have been reported1-12,14-17
. Other locations and types of kissing nevi have been reported less frequently than that of the eyelids: nevus spilus of the eyelids15
, a divided mast cell nevus16
, epidermal nevi of the finger17
, and divided nevi of the penis4-11
The borders that would be united into one and the mirror-image symmetric features are related to its embryologic mechanism. The eyelids start to form at weeks 5~6 of gestation and fuse at weeks 8 to 9 of gestation, then divide again at week 24 of gestation14
. A kissing nevus of the eyelids may originate between weeks 8~24 of gestation. During the fused state, melanoblasts are present at the borderline between the upper and lower eyelids. Subsequently, cellular division continues, and one nevus becomes two lesions that were located on adjacent sites.
Kissing nevi of the penis are extremely rare. The first case was reported by Desruelles et al.4
in 1998, and only 12 cases of kissing nevi of the penis have been described4-11
(). The same mechanisms can be applied to these lesions. Two invaginations appear in the digital edge of the penis from gestational week 11~14. The epithelial glandular placode forms the glandular urethra and the epithelial preputial placode divides and forms the glans and the prepuce4
. Desruelles et al.4
hypothesized that melanoblasts and melanocytes migrate to the lesion before separation of the glans from the prepuce at 12 weeks. He thought that after separation each nevus may develop independently. In contrast, Kono et al.6
suggested that melanoblasts start to migrate just after completion of the invagination of the preputial epithelial placode.
Usually, almost all kissing nevi lesions of the penis are benign melanocytic nevi, except one case reported by Egberts et al.8
in 2007. Although that patient had no family history and was just 30-years-old when melanoma was detected, his lesions grew rapidly and atypical pigmentation was an unusual clinical feature.
Malignant melanoma of the penis is rare, accounting for <2% of primary penile malignancies. Most cases of malignant melanoma of the penis occur in patients in their sixth and seventh decades18
. So, when choosing a therapeutic option for a kissing nevus of the penis, the focus should be on esthetic and functional outcome. Surgical excision and reconstruction by skin grafting using remnant foreskin have been recently performed and showed favorable outcomes10
. However, in cases in which nevi are large, as these lesions, surgical excision may cause a scar and deformity of the glans penis. Mandal et al.19
treated congenital nevocellular nevi with a laser and showed satisfactory esthetic results. In our patient, we concluded that laser treatment was the best method to treat his lesion without complications. But, he denied any further treatment and chose observation.
We report here a rare case of kissing nevus of the penis that showed an obvious mirror-image symmetry relative to the coronal sulcus.