Kissing Nevus of Penis: A Brief Case Report

Kissing nevus is a rare clinical variation of the congenital melanocytic nevi located on adjacent sites of the body at which division occurs during embryogenesis. Kissing nevus is a curious type of nevus that was first described on the eyelids in 1908. These lesions are very rare on the penis; including this case, only 20 patients have been reported to date in the literature. We present one new case of kissing nevus of the penis along with histopathological findings.


INTRODUCTION
Kissing nevus is a rare clinical variation of the congenital melanocytic nevi located on adjacent sites of the body at which division occurs during embryogenesis. Kissing nevus is a curious type of nevus that was first described on the eyelids in 1908 (1,2). These lesions are very rare on the penis; including this case, only 20 patients have been reported to date in the literature. We present one new case of kissing nevus of the penis along with histopathological findings.

CASE REPORT
A 14-year-old male patient applied for circumcision. On physical examination, 1.0 × 1.0 cm and 1.5 × 1.0 cm black colored patches were located, respectively, on the prepuce and the lateral glans penis (Fig.1a), while the coronal sulcus was exempt from melanocytic pigmentation. The lesions overlapped each other when the prepuce was retracted. The patient had no other known illness or family history, and laboratory tests were within normal limits. Removal of the lesion in the prepuce was performed along with circumcision in the same session (Fig.1b). Laser treatment for the glans penis lesion was also planned.
Histopathological examination of the section showed nests of nevus cells with abundant melanin in the dermis under stratified squamous epithelium, and the lesion was reported to be the result of an intradermal melanocytic nevus (Fig. 1c). After two months of follow-up, laser treatment for the lesion on the glans penis was recommended, but the patient did not accept advanced treatment. Similar to kissing nevus on the eyelids, genital lesions originate from a single embryonic developmental lesion, which divides with the development of the external genitalia(5). Reported cases of kissing nevus have almost always histopathologically shown melanocytic nevi; other types of kissing nevus are rarely reported. This includes mast cell tumors and epidermal nevi on the fingers as well as kissing nevus of the penis (6, 7).
The formation of symmetry in the form of a mirror image of the lesions on opposite surfaces can be explained through the embryological mechanism. There are two hypotheses about the embryological mechanism of kissing nevus of the penis. Two invaginations appear in the digital edge of the penis from gestational weeks 11 to 14. The epithelial glandular urethra is composedof the glandular placode, and the epithelial preputial placode divides and forms the glans and the prepuce(4).
Desruelles et al. (4) hypothesized that the problem is caused by the migration of the melanoblasts and melanocytes before completion of the invagination of the preputial epithelial placode. In contrast, Kono et al. (8) suggested that the migration of the melanoblasts occurs just after the embryological separation of the glans from the prepuce, which occurs at 12 weeks.
Because pathological examination results in almost all cases of kissing nevus of the penis in the literature show a benign melanocytic nevus, the primary aim of the treatment should concentrate on aesthetics and functionality.There has been only one case in which the pathological examination results showed malignant melanoma (9). Excision and graft using the patient's prepuce or the oral mucosa of the lower lip is a treatment choice that leaves no loss of sensation and provides good cosmetic results (9,10). But it is obvious that the removal of large lesions entails the possibility of deformity and of scarring of the glans penis. Yun et al. (11) treated kissing nevus of the penis with an Nd:YAG laser.
Conservative treatment and regular follow-up are also reasonable options, because of a certain risk of malignant change in the nevus giving rise to malignant melanoma, a result documented more often for large nevi (12,13).
In our case, the kissing nevus of the penis was treated with circumcision following excision of the preputial lesion. The patient and relatives did not request further treatment, because the results of the pathologic examination were benign. The patient is scheduled for follow-up at regular intervals. a b c