Neurocristic cutaneous hamartoma of the scalp
A 2-month-old girl born of non-consanguineous parents was noted to have a right occipital scalp swelling since birth. It had been biopsied elsewhere, but the procedure was terminated due to excessive bleeding. On examination, a firm 6 × 6 × 2 cm well-defined, right parietooccipital swelling was noted, as was a healing biopsy site. No underlying bony defect was palpable. The anterior fontanelle was lax and pulsatile. The lesion could not be transilluminated. No cough impulse was noted. There were no focal neurological deficits. A general physical examination disclosed no stigmata of neurofibromatosis types 1 or 2, or of neurocutaneous melanosis. The computed tomography (CT) scan of the brain [] showed a large, well-defined, contrast-enhancing, extracranial swelling of the right parietooccipital scalp unassociated with an abnormality of underlying calvarium. Both brain parenchyma and the ventricular system were normal. An ultrasound study of the abdomen showed no abnormality. The child underwent a near total excision of the mass. At surgery, the purely extracranial nature of the mass was confirmed. It was firm and vascular. The underlying bone was normal. The postoperative course was unremarkable. At a 4-month follow-up, no abnormality was evident.\nGrossly, the cut surface showed an ill-circumscribed lesion that was smooth, white and soft with a myxoid appearance. The overlying skin was intact. Histologic examination disclosed fibrous tissue containing well-defined lobules and nests of spindle-shaped cells forming whorls and bundles cytologically appearing schwannian in nature [Figure and ]. Immunohistochemical studies (streptavidin-biotin peroxidise complex method) showed the cytoplasm and nuclei of these cells to be S-100 protein (Dako, Carpinteria, CA, USA, polyclonal, 1:200) reactive. Membranous staining for collagen 4 (Dako, monoclonal, 1:50) was also noted. Focal positivity for CD57 (Novocastra, monoclonal, 1:50) and CD34 (Dako, monoclonal, 1:50) [Figure –] was evident as well. There was no staining of these cells for epithelial membrane antigen (Dako, monoclonal, 1:50), and HMB-45 (Dako, monoclonal, 1:50). Surrounding these nests and merging with them in areas were plump, fusiform cells with oval nuclei, and eosinophilic cytoplasm HMB-45-positive []. A few such cells had shown features of delicate cytoplasmic Fontana–Masson positivity. In areas, the stroma was loose and myxoid, contained delicate vascular channels, minute nerve fascicles, and occasional lobules of adipose tissue. Alcian blue-positive, the stroma was also rich in CD34-positive cells []. The lesion was largely schwannian in character, but contained neurofilament protein (Dako, 2F11, 1:600) immunoreactive axons as well as cells cytologically resembling both melanocytes and nevus cells. Nuclear atypia was absent; the MIB-1 (Dako, 1:20) proliferation index was <1%. There was no evidence of malignancy. Cutaneous adnexae were not present within the lesion. The diagnosis of NCH was confirmed.