Giant Cerebriform Congenital Cellular Blue Nevus Presenting as Cutis Verticis Gyrata.

Sir,

Blue nevus is a neoplasm composed of pigmented dendritic dermal melanocytic cells in the reticular dermis.

A 28-year-old male came to us with multiple swellings over his lower back; the swellings were of a 5-year duration. He gave a history of pigmented patch on his lower back since birth, which has been gradually increasing in size. His family history was negative for a similar problem. Examination revealed a horizontally placed big oval swelling of size 25 cm × 20 cm, occupying the left lumbosacral region that constituted four linear horizontally placed tubular swellings spread across the left lumbosacral region tapering on the right side, crossing the midline. The swellings were separated by furrows, both horizontally and vertically, mimicking cutis verticis gyrata. It was soft to firm in consistency, and was bordered on the right side by hyperpigmentation, hypertrichosis, and follicular atrophy [Figure 1]. Based on the clinical features, plexiform neurofibroma and giant congenital melanocytic nevus were considered in the differential diagnosis. Ultrasonography of the swellings revealed a heterogenously hypoechoeic lesion in his left lower back in the subcutaneous plane, measuring 2.4-3 cm in thickness [Figure 2a]. Magnetic resonance imaging (MRI) showed hyposignal intensity on all signals, suggestive of fibrous and/nerve tissue [Figure 2b]. Biopsy of the lesion revealed groups of melanocytes with monotonous nuclei and spindle cells, with interlacing bundles at the periphery [Figure 3a and b]. Immunohistochemical study using antibodies (CD34 and S100) showed strong expression [Figure 4a and b]. However, human melanoma black (HMB)-45 was not expressed. Histopathology with immunohistochemical study helped in confirming the diagnosis of cellular blue nevus (CBN). In view of the large size, the nevus was labeled giant CBN (GCBN) and the patient was referred to a reconstructive surgeon.

Figure 1

(Original) Multiple linear horizontally placed tubular swellings on the left lumbosacral region intercepted by furrows, bordered by follicular atrophy, hypertrichosis, and hyperpigmentation

Figure 2

(a) (Original) Ultrasonography showing heterogenously hypoechoeic lesion in the subcutaneous plane, measuring 2.4-3 cm in thickness (b) (Original) MRI of the lumbosacral region showing hyposignal intensity on all signals

Figure 3

(a) (Original) Histopathology. Hematoxylin and eosin (H and E) stain. (x 100). Dermis shows groups of melanocytes with monotonous nuclei and spindle cells with interlacing bundles at the periphery (b) (Original) Histopathology. H and E stain. (x 400). Spindle cells showing ill-defined borders with scanty cytoplasm and prominent nuclei. Melanocytes appear as bipolar-and spindle-shaped, with borders showing melanin granules

Figure 4

(a) (Original) Histopathology. (x 100). Immunohistochemistry with antibodies (CD34) showing strong expression (b) (Original) Histopathology. (x 100). Immunohistochemistry with antibodies (S100) showing strong expression

CBN can present in all age groups, although commonly seen in adults younger than 40 years. It usually presents as a bluish black to bluish grey nodule, ranging 1-2 cm in size. However, CBN larger than 10 cm, namely, GCBN, is rare and few cases of this have been reported in the literature [Table 1].[12345] Moreover, GCBN of this size (25 cm × 20 cm) has so far not been reported in the literature.

Table 1

(Original) Published case reports of Giant cellular blue nevus

GCBN resembles giant congenital melanocytic nevus clinically. Nonetheless, histopathologically, GCBN can be differentiated from giant congenital melanocytic nevus by the absence of junctional activity and sparseness of hair follicles in GCBN, whereas an increased number of hair follicles and frequent nevus cell nests at the dermoepidermal junction are seen in the giant congenital melanocytic nevus.[6] Furthermore, strong expression of CD34 and S100, along with histopathology helped in establishing the diagnosis of CBN. Notably, HMB-45 was not expressed by the nevus in the index case, which can be attributed to the lack of melanin in melanocytes (type C melanocytes) in the nevus.

Involvement of the sacrococcygeal region in the index case is in line with the most common site of involvement of CBN. Furthermore, CBN resembling cutis verticis gyrata in the index case is noteworthy. A few cases with such a presentation have been reported in the literature but they were not as major as the case under study. CBN can be locally aggressive and may infiltrate adjacent structures; conversely, malignant degeneration rarely occurs. However, there is no evidence of the infiltration of surrounding structures or malignancy despite the massive size of GCBN in the index case. Incidentally, CBN has malignant transformation potential of 5.2-6.3%.[7] Moreover, it has been associated with melanomas. Granter et al. reported an association with malignant melanoma in two cases of CBN while reviewing the histopathology of 10 cases of malignant blue nevus.[8] Surgery is the only treatment option available for such cases of GCBN and wide excision would be ideal for the index case.