Panda nevus

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A 10-year-old girl presented with an asymptomatic blackish pigmented skin lesion around the left eye since birth, and the lesion had been growing commensurate with the patient’s age. There were no other pigmented skin lesions and no relevant family history. On examination, the skin was darkly pigmented, thickened, and involved the medial three-quarters of the upper and lower lids and the medial canthus of the left eye [Figure 1]. The bulbar conjunctiva and the sclera were normal. The rest of the eye was normal and no visual disturbance was present. A diagnosis of congenital divided melanocytic nevus (Panda nevus) of the eyelids was made.

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Figure 1:

Solitary well defined blackish pigmented plaque noted over medial three quarters of the upper and lower lid and the medial canthus of the left eye.

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An extremely rare congenital dermatological disorder called “Panda nevus,” also known as “kissing nevus,” “split ocular nevus,” and “divided nevus,” develops on the opposing borders of the upper and lower eyelids. It is an uncommon and intriguing embryological phenomenon that Fuchs originally documented in 1919 in German literature.^[1] About 30 cases have been documented since then. In the early embryonic life, when the lids are fused, which is between the 9^th and 24^th week of gestation, the divided naevus is most likely to develop as a single lesion. After the 24^th week of pregnancy, the lids separate, and it appears that during this time, the naevus also separates. As a result, the presence of a divided naevus is regarded as a marker of embryonal development of the naevus since it allows us to guess when melanocytic migration occurred.

These congenital naevi are divided into two distinct classifications. The first classifies the naevus into three sizes: tiny (<1.5 cm in diameter), medium (between 1.5 and 20 cm in diameter), and large (more than 20 cm in diameter). The second describes the histology type (melanocytic, cellular, or compound).^[1] According to the literature, the incidence of malignant changes ranges from 2% to 40%, depending on the length of follow-up, with an average of 14% over a lifetime. None of the divided nevi observed in this literature review had any known instances of malignant change. It is important to note that many authors have used Fuchs’s original 1950 writings, which discuss a malignant transformation in one patient who had previously had surgery.^[2]

Available treatment options include cryotherapy, dermabrasion, and laser therapy. Surgical options include partial or full thickness excision, autologous cultivated medium, split or full thickness surgical graft, local tissue transfer, distant tissue transfer (pedicled flap), and free tissue transfer (oral mucosal graft). The majority of authors consider that if surgical intervention is intended, it should be carried out as soon as feasible to avoid functional issues, including visual abnormalities, untreatable amblyopia (related to ptosis), and epiphora caused by puncta compression. Even a 2-month-old infant has undergone surgery for these abnormalities with positive outcomes. Others have suggested that surgical correction should be performed between the ages of 4–6 years (before entering school) to prevent cruel taunts and allow scars to mature.^[2]

Irrespective of the histology type, surgical treatment often entails a staged reconstruction with full-thickness skin grafts or eyelid flaps to produce satisfactory esthetic and functional outcomes. Small lesions close to the lid margins may benefit from the modified Kuhnt-Szymanowski method.^[3]