Giant Congenital Melanocytic Naevus with Proliferative Nodules Mimicking Congenital Malignant Melanoma: A Case Report and Review of the Literature of Congenital Melanoma

Congenital malignant melanoma (CMM) is a rare condition that is defined as malignant melanoma recognized at birth. CMM may develop in utero in one of three ways: (1) transmission by metastasis through the placenta from a mother with melanoma; (2) primary melanoma arising within a giant congenital melanocytic naevus (GCMN); (3) primary de novo cutaneous CMM arising in utero. CMM can be confused clinically and histologically with benign proliferative melanocytic lesions such as giant congenital nevi. We describe the case of a patient presenting a GCMN with proliferative nodules, clinically and dermoscopically resembling a CMM, demonstrating the importance of caution in making a diagnosis of MM and highlighting the possibility that benign lesions as GCMN can mimic a malignant melanoma in this age group. 1. Case Report A 7-day-old Italian male child showed at birth a dark, irregular, and raised skin lesion measuring 8 × 11？cm located on the back (Figure 1). He was born full-term by cesarean delivery. The birth weight was 3200？g. He appeared otherwise healthy with no evidence of lymphadenopathy or organomegaly, with an Apgar score of 10. The mother was 30, and she was healthy and received no pharmacological therapies during the pregnancy. There were no maternal suspicious lesions. One month before the delivery, a presumable angiomatous lesion was diagnosed by prenatal ecography. No history of melanoma was known in the family. There were two brothers, without any disease. At the age of 7 days, he was seen at the Department of Dermatology of Federico II of Naples because, according to clinical features of the lesion, there was a very strong suspect of melanoma. A careful dermoscopic examination was performed, which revealed irregular pigmentation, atypical pigment network, irregular dots and globules, irregular streaks, and a wide blue-whitish veil (Figure 2). On the seventh and fourteenth days of life, 4 biopsy specimens of the flat and the raised areas were taken. The specimens were fixed in formalin and sent for histologic analysis. All specimens demonstrated similar histologic features. There was (Figures 3(a), 3(b), and 3(c)) a dermic component characterized by a solid growth pattern with deep melanocytic nodules showing a high hypercellularity with no significant atypia. The melanocytes were densely packed and uniform in nature exhibiting a small nucleus, sometimes with fine nucleoli. Nuclear pleomorphism was not seen. The immunohistochemical stains showed a strong positivity for S-100 protein (Figure 3(d)) and ki67 (Figure 3(e)), while the HMB-45 (human