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  • Onychopapilloma is an uncommon benign

    2018-11-03

    Onychopapilloma is an uncommon, benign neoplasm of the nail bed, first described by Baran and Perrin in 1995; the term onychopapilloma was coined in 2000. The clinical features of onychopapilloma are nonspecific. The most common clinical presentation is longitudinal erythronychia, but many other clinical presentations including longitudinal leukonychia, long splinter hemorrhages, short splinter hemorrhages, and longitudinal melanonychia have been reported. Among these various clinical presentations, onychopapilloma presenting as longitudinal melanonychia has been reported in only two case series and one original article. The disease is histopathologically characterized by matrix metaplasia of the nail bed epithelium, acanthosis, and papillomatosis of the distal nail bed epithelium, and in some cases, multinucleated cells. Gee et al raised a question about the histopathological criteria proposed by Baran and Perrin and claimed that a typical clinical picture with subungual keratosis is sufficient for diagnosing the disease. Histopathologically, the differential diagnosis of onychopapilloma includes, Bowen disease, onychomatricoma, and seborrheic keratosis. Bowen disease is characterized by atypical ikk inhibitor and dyskeratotic cells. Onychomatricoma is a fibroepithelial tumor of the nail matrix, characterized by filiform epithelial projections invaginating into the stroma. Ungual seborrheic keratosis is characterized by pseudo-horn cysts and is not associated with matrix metaplasia. In the present case, although the nail matrix was not fully included in the specimen, diagnosis of onychopapilloma was made based on clinically longitudinal melanonychia, no recurrence after nail bed resection, and distinctive histological features of the nail bed. The etiopathogenesis of onychopapilloma is unknown. In this case, we could not find any evidence of human papillomavirus (HPV) infection. We performed an HPV DNA chip test, and concluded that the lesion may be not associated with HPV infection on the basis of negativity for this test. HPV staining was also negative on the biopsy specimen in other case series. Therefore, we postulate that onychopapilloma is not associated with HPV infection. In the present case, the patient\'s history was uneventful, and he did not recall any trauma to the nail. It is worthy of note that he had been treated with ustekinumab for ankylosing spondylitis and had a history of heavy hand use because of his job as a neurosurgeon. Further study is warranted to determine the etiology of onychopapilloma including social history and medical history. Racial difference in the prevalence of onychopapilloma is not yet established. Tosti et al described that most patients with longitudinal erythronychia and longitudinal leukonychia had Fitzpatrick 1–3 phototype, whereas all the patients with longitudinal melanonychia had Fitzpatrick 4–6 phototype. Although Asians were not analyzed in that study, presentation of onychopapilloma may vary in different ethnic groups. Recently, onychopapilloma presenting as longitudinal melanonychia was observed in a 37-year-old Japanese woman. Although there are only rare reports about onychopapilloma presenting as melanonychia, it is possible that onychopapilloma presenting as longitudinal melanonychia may not be so rare in the Fitzpatrick 4–6 phototype, including Asians. The reason why onychopapilloma induces melanonychia is melanocytic activation rather than melanocytic hyperplasia. The first explanation of this was that melanocytes in the matrix stained positively for HMB-45 in a case reported by Miteva et al and the present case. This stain identifies only active melanocytes. Another explanation is that, because melanonychia was limited to the lesion, we can assume that the tumor in the distal nail matrix activated the adjacent melanocytes and induced pigmentation of the ventral nail plate.
    Pilomatricoma (PM) is a benign adnexal tumor thought to be derived from hair matrix cells. It commonly occurs in the head and neck region of younger individuals as a superficial, firm, solitary, and slowly growing mass with a diameter ranging from 0.5 cm to 3 cm. PM is associated with activation of the Wnt β-catenin signaling pathway caused by either a mutation in the adenomatous polyposis coli (APC) gene or the β-catenin gene. Rarely, it grows larger than 5 cm and is termed giant PM (GPM). GPM occasionally grows rapidly and often displays unusual clinical manifestations reminiscent of metastatic tumors. Histologically, it frequently shows features suggesting the possibility of malignancy in addition to the findings of common PM. From these clinicopathological distinctions from the common PM, it is likely that further pathobiology other than the activation of Wnt β-catenin signaling is taking place to form this characteristic condition. However, etiology of GPM is yet to be clarified. Here, we report a case of GPM where histological evaluation and immunohistochemical analysis were performed.