CVG is a disease characterized by the formation of sulci and gyri that resemble those of the cerebral cortex. CVG is categorized as primary essential, primary non-essential, or secondary depending on the intrinsic etiology. Primary essential CVG is an isolated discovery and has nothing to do with any neurological or ophthalmological disease. This type usually predominates in male patients during or after puberty and is usually distributed symmetrically, mainly affecting the vertex and occipital region . Primary non-essential CVG is usually associated with neurological and ophthalmological disorder, such as intellectual disability, epilepsy, deafness, cataracts, strabismus and blindness . The clinical presentation of secondary CVG varies depending on the underlying cause, including hormone-related diseases such as acromegaly, pituitary tumors, thyroid diseases, or myxedema; cutaneous inflammatory such as tuberous sclerosis, eczema, psoriasis, acne conglobate, or Darier disease; infectious diseases such as syphilis or human immunodeficiency virus; neoplasms diseases such as leukemia, or T-cell lymphoma [4, 5, 7, 10, 15, 16]. The histopathology of the primary CVG will reveal hypertrophy and hyperplasia of epidermal appendages and thickened dermal collagen in skin, whereas the histopathological changes in secondary CVG shows abnormalities characteristic of the underlying etiology . The pathogenesis of primary CVG are still unclear. Although some familial forms with autosomal dominant condition or recessive inheritance with variable expression have been reported, the majority of cases of primary essential CVG are sporadic . Due to the hyperplasia of dermal collagen in CVG, some authors believe that it is an autosomal dominant condition caused by mutation in the FGFR . The FGFR2 gene encodes a transmembrane tyrosine kinase and can function as a mitogenic, angiogenic or inflammatory factor, which may be involved in the pathological process of CVG . It is not difficult to make a diagnosis of CVG based on clinical manifestations, but it is necessary to draw our attention to distinguish these three forms. For any of the above three forms of CVG, the other two must be excluded before making the final diagnosis (Fig. 5). In most cases, primary CVG is asymptomatic, except for some neurological and ophthalmological symptoms. In addition, the operation is invasive, so clinical observation is a good treatment choice for patients with stable disease or mild symptoms. However, surgical treatment, such as partial excision, staged excision, skin grafting, local flap grafting, free flap grafting and tissue expansion may also be performed when there is an aesthetic demand. For small and local lesions, partial scalp excision and skin or flap grafting can be selected. Tissue expansion and staged excision are excellent options for larger scalp lesions. Some scholars once reported a technique combining a “butterfly”-shaped scalp skin excision design and sub-galeal scalp relaxation incisions to effectively improve the appearance of the scalp . In contrast, secondary CVG usually regresses after treatment of the underlying disease, although surgical excision may be necessary sometimes.
The postoperative pathological results of the above patient we reported showed that there were dense intradermal melanocytic nevus, therefore, the patient was diagnosed with secondary CVG caused by CIN. CIN is one of several benign tumors that cause CVG, accounting for 12.5% of CVG cases and there is a female predilection . Hammond first described a cerebriform naevus resembling CVG in 1937 . It is usually congenital but can also be acquired. CIN most commonly occurs in the parietal and occipital areas of the scalp, and the frontal and temporal areas are less involved . These nevus appear as a small spot, a small protuberant mass, or a patch of alopecia at birth or early in life. Over time, the lesions slowly expand and become more prominent, which was consistent with our patient's condition. The size of CIN lesions usually ranges from 3.0 × 2.0 cm to 25.0 × 22.5 cm . Patients often present with progressive alopecia, occasionally accompanied by tenderness, itching, burning, and repeated infections. In the case we reported, the hair loss area of the patient was only accompanied by mild itching, and there was no tenderness, burning, or ulcer infection. The diagnosis of CIN is based on clinical and histopathological examinations. Therefore, CIN must be differentiated from other conditions that manifest as CVG, including primary CVG and secondary CVG caused by other reasons. CIN may evolve into malignant melanoma(MM), which can even appear early in life. Orkin reviewed 50 cases of CIN reported up to 1974 and found that two cases of MM were derived from CIN. One of them was a 6-year-old boy whose entire lesion was excised and grafted, and there was no sign of recurrence 11 years later . The other was a 51-year-old woman who died 10 months later, despite chemotherapy and radiotherapy. Hayash reviewed 17 cases of CIN reported from 1974 to 2008 with one case of MM from CIN. This patient was a 66-year-old man whose entire lesion was excised and received chemotherapy, with no recurrence during a 6-month follow-up. Therefore, Hayashi found the frequency of MM alteration of CIN to be 4.5% (3 of 67 cases) . Here we searched the relevant available literature reported from 2008 to 2020 from three databases: PubMed, Web of Science, and the Cochrane Library. Search terms used were 'cutis verticis gyrata' or 'cerebriform intradermal nevus'. The language was restricted to English. Furthermore, we reviewed reference lists from retrieved articles to appraise other potential studies. In finally, we found a total of ten CIN patients, with no case of MM from CIN (Table 1). Including these added cases, we estimated that the risk of CIN transforming to MM was 3.9% (3 of 77 cases). Even though, we must realize that there is no a precise and completed computerized search for all relevant available articles published up to 2020. The calculation of malignant transformation risk is not so accurate that more future cohort studies or a true systematic review are needed. Because of the the possibility of developing MM and aesthetic demand, surgical excision of the lesion is recommended. However, considering the low risk of malignant transformation of CIN and the surgical excision of the lesion usually involves extensive mutilation, Van Geest et al. recommended a wait-and-see policy . Nevertheless, for those CIN patients who have not undergone surgery to excise the lesion, close follow-up is still very necessary (Fig. 6).