Romero Laura S, Park Helen, Shoaee Noushin, Cohen Philip R
Dermatology, University of California - San Diego, San Diego, USA.
Medicine/Dermatology, Veterans Administration Medical Center, San Diego, USA.
Cureus. 2020 May 3;12(5):e7946. doi: 10.7759/cureus.7946.
Onychomatricoma is a rare, benign nail matrix tumor. It most frequently occurs on one of the first three fingers of the dominant hand or the big toe in middle-aged women. Our patient presented with a 10-year history of a progressive thickening of her right great toenail; it bled easily and was intermittently painful. She had experienced trauma to the nail prior to the onset of the dystrophy. MRI primarily showed inflammation localized to the nail bed without bony extension. Excisional biopsy, which included both the nail plate and matrix, established the diagnosis of onychomatricoma originating from the ventral nail matrix (lunula). Nail trauma or fungal infection may have a causative role in the pathogenesis of onychomatricoma. The nail plate can show splitting, increased curvature, or ridging; it can also present with yellow, red or brown, linear, pigmented bands. The clinical differential diagnosis of onychomatricoma includes fibrokeratoma, melanonychia, onychomycosis, periungual fibroma, and squamous cell carcinoma. Dermoscopic imaging shows parallel lesion edges and splinter hemorrhages; these dermoscopic features support the diagnosis of onychomatricoma over squamous cell carcinoma. Imaging such as ultrasound or MRI may suggest the diagnosis. Biopsy of the tumor is necessary to establish the diagnosis; the tumor may derive either from the ventral nail matrix (lunula) or from the ventral surface of the proximal nail fold. Histologic features vary depending not only on tumor origin but also on tissue orientation. Proximally, there is a fibroepithelial tumor consisting of fibrous stalk pierced by epithelial invaginations; the epithelium shows matrical differentiation containing basal and prekeratogenous cells. Distally, the tumor pierces the nail plate as glove-finger digitations; these digitations appear as discrete villi in the nail plate or show their negative image as multiple empty channels that have been described as "worm holes". The channels may be epithelial lined and contain serous fluid. It is important to obtain an adequate biopsy specimen; the distinctive fibroepithelial histology might be inapparent in partial specimens lacking the epithelial invaginations. Immunohistochemical staining can distinguish onychomatricoma from tumors that can mimic its pathologic changes: fibromyxoma, neurofibroma, and perineurioma. Complete surgical excision is generally curative.
甲母质瘤是一种罕见的良性甲母质肿瘤。它最常发生于中年女性优势手的前三指之一或大脚趾。我们的患者有右大脚趾指甲渐进性增厚10年的病史；该指甲容易出血且间歇性疼痛。在甲营养不良开始之前，她的指甲曾受过外伤。磁共振成像（MRI）主要显示炎症局限于甲床，无骨质延伸。切除活检，包括甲板和甲母质，确诊为起源于甲母质腹侧（甲半月）的甲母质瘤。指甲外伤或真菌感染可能在甲母质瘤的发病机制中起致病作用。甲板可出现裂开、曲率增加或嵴状；也可出现黄色、红色或棕色的线性色素沉着带。甲母质瘤的临床鉴别诊断包括纤维角化瘤、甲下黑素沉着、甲癣、甲周纤维瘤和鳞状细胞癌。皮肤镜成像显示病变边缘平行和裂片样出血；这些皮肤镜特征支持甲母质瘤的诊断而非鳞状细胞癌。超声或MRI等影像学检查可能提示诊断。肿瘤活检对于确诊是必要的；肿瘤可能起源于甲母质腹侧（甲半月）或近端甲襞的腹侧表面。组织学特征不仅因肿瘤起源而异，还因组织方向而异。近端，有一个纤维上皮性肿瘤，由被上皮内陷穿透的纤维蒂组成；上皮显示甲母质分化，含有基底细胞和角质形成前细胞。远端，肿瘤以手套指状突起穿透甲板；这些指状突起在甲板中表现为离散的绒毛，或显示其负像为多个被描述为“虫洞”的空通道。这些通道可能内衬上皮并含有浆液。获取足够的活检标本很重要；独特的纤维上皮组织学在缺乏上皮内陷的部分标本中可能不明显。免疫组织化学染色可将甲母质瘤与可模仿其病理变化的肿瘤区分开来：纤维黏液瘤、神经纤维瘤和神经束膜瘤。完整的手术切除通常可治愈。
