甲板干细胞瘤是一种通常表现为纵向甲板增厚的甲翘肿瘤，涉及部分或全部甲板。组织病理学上，其特点是增殖的甲基基质的深腹穹窿和CD34+和CD10+纺锤细胞的增殖，伴有胶原性到黏液样的间质。甲板干细胞瘤被认为是一种纤维上皮肿瘤。近期，通过阵列比较基因组杂交方法验证了RB1基因的缺失。本研究使用形态学方法调查了甲板干细胞瘤中RB1基因的情况。研究纳入了6名甲板干细胞瘤患者。使用免疫组化染色和原位杂交检测评估了RB1基因的情况。免疫组化染色显示，所有的六例都在甲板干细胞瘤的间质成分中经历了RB1基因缺失，而在增殖的甲基基质中没有发现。在五例患者的原位杂交检测中，显示出RB1基因座的等位基因缺失，在间质成分中发现，但在增殖的甲基基质中未见缺失。RB1基因缺失仅在甲板干细胞瘤的间质成分中观察到。我们的发现表明，甲板干细胞瘤中的增殖的甲基基质代表了与肿瘤性间质增殖相关的反应性增生。这表明甲板干细胞瘤应该被视为一种RB1基因缺失的软组织肿瘤，而不是纤维上皮肿瘤。© 2023 John Wiley & Sons A/S. 由John Wiley & Sons Ltd出版。

Onychomatricoma is a nail neoplasm that usually presents as longitudinal nail plate thickening, involving either the partial or whole nail. Histopathologically, it is characterized by deep invaginations of the proliferating nail matrix and proliferation of CD34+ and CD10+ spindle cells with collagenous to myxoid stroma. Onychomatricoma has been considered a fibroepithelial neoplasm. Recently, RB1 loss has been verified using array comparative genomic hybridization.This study investigated the RB1 status in onychomatricoma with morphological methods.Six patients with onychomatricoma were included in the study. RB1 status was assessed using immunohistochemical staining and fluorescence in situ hybridization. Immunohistochemical staining showed that all six cases experienced RB1 loss in the mesenchymal component of onychomatricoma but not in the proliferated nail matrix. Fluorescence in situ hybridization in five cases showed a monoallelic deletion of the RB1 locus in the mesenchymal component but not in the proliferated nail matrix.RB1 loss was observed only in the mesenchymal component of onychomatricoma. Our findings suggest that the proliferated nail matrix in onychomatricoma represents reactive hyperplasia of various degrees secondary to neoplastic mesenchymal proliferation. This indicates that onychomatricoma should be recognized as an RB1-deleted soft tissue neoplasm rather than a fibroepithelial neoplasm.© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.