Abstract
Introduction: Melanotic neurofibromas are rare tumours, derived from peripheral nerve sheath, whose originality consists in the presence of melanic pigment. The clinical and histological diagnosis is often difficult to make requiring the immunohistochemical exam to make the difference between melanotic neurofibroma and the other pigmented tumors. Melanotic neurofibroma has a good prognosis and the malignization is rare. Case Report: A 22 year-old man presented since childhood a left occipital tumor, it had a firm consistency and pigmented color. CT objectified isodense occipital mass, which enhanced heterogeneously after contrast product. Lack of bone loss beside. Complete surgical excision was performed. Histological and immunohistochemical analysis led to the diagnosis of melanotic neurofibroma. Discussion: Pigmented neurofibroma is a rare variant of neurofibroma showing melanin production and constitute less than 1% of all cases. It can occur on their own or be associated with neurofibromatosis. They must be distinguished from classical neurofibromas when pigmentation occurs in the latter. Melanotic neurofibromas usually appear in the second or third decade of life and rarely in childhood. The clinical diagnosis is difficult to establish requiring the histopathological examination to differentiate between the melanotic neurofibroma and other pigmented tumours. It can mimicking a giant naevus or a neurocristic cutaneous hamartoma. These are the two main differential diagnoses among children. Among adults, the main difficulty is to distinguish melanotic neurofibroma from pigmented dermatofibrosarcoma. The elective treatment is surgical, represented by the complete excision of the tumor. Conclusion: Pigmented neurofibroma is a unique subtype of neurofibroma which is rare and contains melanin producing cells. The histopathological features with unique pattern of melanogenesis, ultrastructural findings and immunohistochemistry will enable us to diagnose this entity and differentiate it from other pigmented tumours of skin.
Highlights
Melanotic neurofibromas are rare tumours, derived from peripheral nerve sheath, whose originality consists in the presence of melanic pigment
Pigmented neurofibroma is a unique subtype of neurofibroma which is rare and contains melanin producing cells
Pigmented or melanotic neurofibroma is a rare variant of neurofibroma
Summary
Melanotic neurofibroma named pigmented neurofibroma is a rare tumor, representing less than 1% of all neurofibromas. In a study of 17 patients who had one or more melanotic neurofibromas, 8 of them had neurofibromatosis type 1 [1] It is a benign spindle cell tumor containing melanin granules. Cellular blue nevus consists of pigmented dendritic cells and fusiform cells organized in nodular pattern. This proliferation is denser and nodular than melanotic neurofibroma [8]. Its originality is the presence of abundant melanin pigment within the neurofibromatous proliferation It is contained in the form of granules intracytoplasmic in dendritic cells, spindle or more rounded cells, which tend to cluster, especially in the deep dermis.
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