A 15-year-old boy presented with large cerebriform hyperpigmented plaque over scalp

Dr. Yasmin Ara Zaman: A 15-year-old boy 4th issue of a non-consanguineous parents presented with a history of multiple plaques and patches on the scalp, trunk, upper and lower extremities since birth. Initially, the plaques and patches were smaller in sizes, dark brown in color, painless and non-pruritic. Since 4th year of his age, these plaques start increasing in size and color turned into black gradually (Figure 1). The lesion on the scalp became a giant cerebriform plaque that involved left parietal region. Lesions on the trunk, upper and lower extremities became polysized and polyshaped hyperpigmented papules and nodules. He had no history of headache or seizure. His vision and hearing were normal. He had no evidence of mental retardation. His bladder and bowel habits were normal.

X-Ray chest posteroanterior view and ultrasonography of whole abdomen were normal. X-ray skull occipito-frontal and lateral view revealed a large lobulated soft tissue opacity on scalp overlying left parietal and occipital region. There was sclerosis of the left parietal bone.
Skin biopsy was done and specimens were collected from two sites from the lesion on scalp and trunk. Histopathologic findings of both samples revealed mild hyperkeratosis, nests of nevus cells in the basal layer and in dermis extending to the deep reticular dermis, peri-adnexal and perineural areas ( Figure  2). It was diagnosed as congenital melanocytic nevus.
Magnetic resonance imaging were taken (axial T1WI, T2WI and T1Wl contrast; coronal T2WI, T1Wl contrast; sagittal T1W1 and T1W1 contrast; FLAIR and DW Image) ( Figure 3). There was diffuse lobulated T1WI iso, T2WI and FLAIR hyperintense lesion at the left side of scalp overlying left fronto-temporo-parieto-occipital region and left side of the forehead. The lesion crosses the midline in its posterior aspect. No restricted diffusion was seen on DWI. After IV contrast (Gd-DTPA) administration, strong homogenous enhancement was noted. No abnormal signal change was there in the underlying bone.
Post auricular (about 15 x 0.8 mm) and intraparotid (12 x 0.8 mm) enlarged lymph nodes were present. The ventricles were of normal size, configuration and position for a patient of this age. Extra ventricular cerebrospinal fluid spaces and basal cisterns were unremarkable. The brain stem, cerebellum, sella, parasellar structures and orbits revealed no abnormality. Paranasal sinuses were normal.

Provisional Diagnosis
Congenital melanocytic nevus

Cutis verticis gyrata
Dr. Harasit Kumar Paul: Cutis verticis gyrata is a condition where scalp skin is hypertrophied and folded as parallel or gyrate folds anteriorly to posteriorly. The lesions look like cerebral gyri. 1 Males are commonly affected with primary disease. So, cutis verticis gyrata may be a differential diagnosis. But the affected scalp appears normal on histology in cutis verticis gyrata. 2 There are reports that congenital melanocytic nevus may be present in association with cutis verticis gyrata. 3  on the trunks and arms. The lesions can be emptied by firm pressure. 7 These features are absent here.

Dr. Shourav Dutta: Cylindroma (turban tumor) should be a consideration.
Dr. Paul: This is a benign neoplasm of adnexal origin. There may be single or multiple plaques or nodules located usually on the scalp but may be on the neck, trunk and genitalia. Multiple nodules on scalp may enlarge and coalesce to form giant mosaic plaques referred to as turban tumor. 8-10 Turban tumor itself or as a part of Brooke-Spiegler syndrome may have clinical similarity with the present case.

Discussion
Dr. Paul: Congenital melanocytic nevus is a pigmented melanocytic nevus present at birth. Initial lesion may be pigmented patch. 11 This is a benign condition. This is a clinical condition where there is a non -neoplastic proliferation of abnormal mixtures of tissue's normal components. 1-2% of newborns may be affected with single lesion of congenital melanocytic nevus with a female to male ratio of 1.2:1. Multiple lesions may be there. Sometimes skin lesions may not present at birth, develop at any time after birth and continue to grow over time. Some cases may be associated with other diseases like neurofibromatosis type 1. 12, 13 According to their sizes congenital melanocytic nevus are classified as small (<1.5 cm), medium (1.5-19.9 cm) and large or giant naevi (>20 cm). 11 Dr. Lutfar Rahman Rahat: Is there any genetic linkage in the etiology?
Dr. Zaman: The disease is associated with somatic mutation in utero. 12

Final Diagnosis
Congenital melanocytic nevus