Metastatic Melanoma in a Child with Giant Congenital Melanocytic Nevus.

Sir,

A 13-year-old boy presented with giant congenital melanocytic nevus (GCMN) involving the trunk circumferentially with multiple satellite nevi all over the body since birth [Figure 1a]. The patient had a history of an episode of seizure 2 months back. Cutaneous examination revealed a GCMN covering the entire trunk and multiple smooth, firm, mobile nodules of varying sizes over the back ranging from 3 × 3 cm to 1 × 1 cm [Figure 1b]. A single well-defined, pigmented, annular plaque of size 2 × 1.5 cm was present on the back. MRI brain showed T1 hyperintense, T2 hypointense lesion with blooming on T2*, no diffusion restriction, surrounding edema, and mild mass effect, and no leptomeningeal involvement [Figure 2]. Imaging appearance suggested the impression of metastatic melanoma. The patient underwent right frontoparietal craniotomy with excision of the space-occupying tumor which on histopathological examination (HPE) revealed sheets of round to polygonal pleomorphic cells with eosinophilic cytoplasm and abundant melanin within the cytoplasm [Figure 3a]. Eccentrically placed vesicular nucleus with prominent nucleolus were seen on high resolution, and mitotic figures around 1–2/high power field were seen [Figure 3b]. A single hyperpigmented plaque over the back was biopsied, which on hematoxylin and eosin staining revealed basal melanosis and nests of melanocytes scattered individually with admixed nevus cells [Figure 3c]. Melanocytes showed prominent hyperchromatic nuclei, the pigment was seen extending beyond the adnexa, and high mitotic activity was noted. These findings were suggestive of malignant melanoma (MM) [Figure 3d].

Figure 1

(a) Clinical picture showing GCMN affecting the trunk. (b) Multiple nodules and a single hyperpigmented plaque is seen on the back over the GCMN

Figure 2

MRI brain showing a lesion which was T1 hyperintense, T2 hypointense with blooming on T2*, no diffusion restriction, surrounding edema

Figure 3

(a) Sheets of pleomorphic cells with eosinophilic cytoplasm and melanin within (hematoxylin and eosin × 10). (b) Eccentrically placed vesicular nucleus with prominent nucleolus and mitotic figures (hematoxylin and eosin × 40). (c) Histopathology of plaque lesion showing basal melanosis. Dermis shows melanocytes arranged in nests with nevocytes (hematoxylin and eosin × 10). (d) Individual melanocytes showing prominent hyperchromatic nuclei with some showing eosinophilic nucleoli (H and E × 40)

Giant congenital melanocytic nevus (GCMN) is an uncommon type of congenital melanocytic nevus (CMN) with a size of more than 20 cm and occurs approximately in 1 in 2–5 lakh live births.[1] GCMN carries the risk of the development of melanoma. The 5-year cumulative risk of developing MM in GCMN has been estimated to be about 4.5%.[2] We are herewith reporting a rare case of GCMN with metastatic melanoma involving the cerebral parenchyma, and the primary was detected as MM of the skin over GCMN on the back.

Risk factors associated with the development of cutaneous melanoma in GCMN include young age, the presence of multiple satellite nevi, and nevi located over the posterior axis.[3] A study by DeDavid M, et al.[2] has shown that out of 50% cases of GCMN, primary cutaneous MM within the lesion of GCMN was diagnosed before 5 years of age, and the median age of diagnosis of MM was 4.6 years. Our case was diagnosed as GCMN with cutaneous MM with metastasis to the brain parenchyma. In accordance with revised Fox's definition of neurocutaneous melanosis (NCM),[4] in this case, NCM was ruled out. The best in vivo imaging method to demonstrate leptomeningeal melanosis (LMM) is MRI with T1- weighted images. Currently, the patient is asymptomatic and is under whole-brain radiotherapy. We report this case because of the rarity of GCMN and to highlight the need for evaluation for melanoma in GCMN cases.

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Conflicts of interest

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