Giant Congenital Melanocytic Nevus with Occipital Encephalocele: A Very Rare Association.

Sir,

Giant congenital melanocytic nevus (GCMN) is a rare disorder affecting 1 in 200,000–500,000 live births.[1] It is regarded as giant when it involves more than 20 cm in greatest dimension or >9 cm in the scalp or more than 6 cm in the trunk.[2] In about 82% cases, the disease is axially distributed. Central nervous system (CNS) defects such as spina bifida, meningocele, Dandy Walker malformation may accompany it and thus cause significant morbidity.[3] There is an increased risk of malignancy ranging from 4.5% to 12%. Here, we report a case of a GCMN with some unusual associations.

A 5-month-old male child with uneventful ante and postnatal history presented with an extensive pigmented growth involving the scalp, left side of the face, neck, upper trunk, and left shoulder with multiple satellite lesions. Many neurofibroma (NF) like-nodules were present over chin, left ear, cheek, nose, and anterior chest. Multiple lentiginous lesions were scattered over a less pigmented background. A large, soft, pigmented growth was also present over the occipital region just left to the midline [Figure 1]. The swelling was nontender, nonpulsatile, fluctuant & transilluminant with a broad base [Figure 2]. Developmental milestones were not delayed and neither there was any neuro-deficit. Three biopsies were done; one from scalp mass, the second one from melanocytic plaque of anterior chest, and the third one from nodules over the melanocytic plaque. All lesions revealed nevus cells forming nests in the dermo-epidermal junction, upper and mid-dermis, and around the hair bulb. Cells were homogenous without nuclear atypia. There was no pleomorphism, mitoses, or pagetoid spreading into the epidermis [Figure 3]. All of these histological features were consistent with CMN without any evidence of malignant transformation.

Figure 1

Giant congenital melanocytic nevus involving the scalp, left side of face, neck, upper trunk, left shoulder with multiple nodules, satellite lesions and occipital encephalocele

Figure 2

Giant congenital melanocytic nevus posterior view to demonstrate the encephalocele

Figure 3

Multiple nevus cells in nests and sheets with melanophage in papillary and reticular dermis (×200)

A computerized tomography (CT) scan of the large scalp mass demonstrated an encephalocele with evidence of herniation of very thin looking redundant brain tissue into the sac. CT scan image also revealed a significant defect of the occipital bone. We have diagnosed it as an encephalocele covered with a plaque of melanocytic nevus, associated with brain tissue herniation. NF like nodules was confirmed as melanocytic nodule with neurotization. Encephalocele, where the cranium fails to fuse is same as that of spina bifida. Through this defect meninges herniates with or without brain tissue. In encephalocele, CNS structures lie in communication with cerebrospinal fluid pathways.

There are reports of bathing trunk nevus in association with NF type 1, but many cases too had melanocytic nevus with neurotization as in our case. Twenty-six such associations were reported by Heuer[4] Silfen et al., in 2002. Clinical and histopathological similarities between CMN and NF is probably due to common origin of melanocytes and Schwann cell from the neural crest.[5] The term neurotization refers to the resemblance of some melanocytic cells to peripheral nerve sheath cells.

In spite of an extensive search in popular online archives, we found only single case report of GCMN with encephalocele by Shermak et al., from Baltimore.[6] Probably no such association has been reported before from India.

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Conflicts of interest

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