Cerebriform intradermal nevus: A rare entity and its associations.

Cerebriform intradermal nevus (CIN) is a rare form of cutis verticis gyrata (CVG) clinically manifesting as a scalp deformity resembling surface of the brain, with cerebriform morphological characteristics.[1] Hammond and Ransom first described a cerebriform nevus resembling cutis verticis gyrata in 1937.[2] CIN is a nodular nevus cerebriform on its surface, and intradermal histologically.[3] CIN is one of the diverse and rare cause of CVG (secondary/pseudo)[4] characterized by development of folds and furrows, conferring to the tumor a corrugated or convoluted appearance.[3]

CIN is considered as a rare form of congenital melanocytic nevus developing on the scalp.[15]

It usually presents at birth or early life.[13] The mechanism for the cerebriform pattern on the surface of CIN is unknown. There may be multifocal hyperplasia of the epidermis and nevus cells.[3]

Females are more likely to develop CIN. Clinically it presents as asymmetric, skin-colored or slightly pigmented tumor usually localized in the parietal or occipital areas of the scalp. Lesions rarely occur on cutaneous sites other than scalp.[3] Over the years, it slowly enlarges and becomes more prominent and well demarcated with a cerebriform surface. Its size varies from 2 × 3 cm to 25 × 22.5 cm, and at times affects one half to three quarters of the scalp.[3] Progressive alopecia is common, with hair being particularly sparse over the convolutions, and tufts emerging from the sulci. Patients may also have pruritus, tenderness, burning, recurrent infection, bleeding and a fetid and or musty odor.[1] Pregnancy, hysterectomy, surgical exploration, and hormonal activity may induce a growth spurt of CIN. It is suggested that increased hormonal activity may potentiate the growth of these lesions, as growth spurt is often noted at puberty.[14]

Histological examination shows intradermal nevus cells present in the full thickness of the dermis which can be well delineated or irregular. Nevus cells contain varying amounts of melanin. Neuroid transformation can be present in the deeper parts of the lesion with increased collagen fibers simulating those observed in neurofibroma. The nests and nevus cells are observed merging with the neuroid tissue. Hair follicles may appear atrophied, with nevoid tissue densely abutting them.[146]

CIN lesions have high risk for the development of malignant melanoma. The life-time incidence of melanoma arising in a giant nevus or in smaller nevi is 6.3% and 12%. The melanoma may be present at birth, or it may arise in infancy or later in life. The mortality of such lesions is high.[1346]

Patients with CIN have a normal range of intelligence and no local or systemic diseases have been observed.[124] Giant CIN may be associated with a number of systemic diseases.[7] CIN has been related to giant congenital melanocytic nevus. However, the risk of neurocutaneous melanosis in patients with CIN has not yet been established.[4] Association of epidermolytic hyperkeratosis and CIN of the scalp is reported.[8]

Clinically, CIN must be differentiated from other conditions that manifest as CVG such as primary CVG, which is frequently accompanied by neurological or endocrinological anomalies, and secondary CVG resulting from neoplastic or metabolic disorders such as neurofibroma, dermatofibroma, amyloidosis, or myxedema. Other differential diagnosis include leukemic infiltrates in the skin, Ehlers–Danlos syndrome, cerebriform sebaceous nevus, pachydermoperiostosis, aplasia cutis congenita, alopecia mucinosa, cerebriform epithelial connective tissue hamartoma, cylindroma, acromegaly, inflammation, traction and persistent and repeated rubbing of the skin of the scalp with secondary thickening of the connective dermal tissue in mentally retarded subjects.[12]

Early diagnosis and treatment of CIN is important as the risk of development of malignant melanoma is high.[6] Therapeutic possibilities are surgical excision(complete/partial) and plastic reconstruction, sometimes involving tissue expansion techniques.[2] In cases where excision is not possible, close follow-up of the lesion is mandatory.[1]