Stewart Campbell L, Sobanko Joseph F, Rubin Adam I
Department of Dermatology, Hospital of the University of Pennsylvania, Philadelphia, PA.
Am J Dermatopathol. 2015 Jun;37(6):473-6. doi: 10.1097/DAD.0000000000000270.
A 57-year-old woman presented with a 3-year history of a thickened, yellowed, over-curved nail plate of the left second toe. The proximal nail fold had an associated nodule. When observed head-on, the distal nail plate demonstrated multiple circular perforations. Avulsion of the nail plate revealed a 0.7 cm pale white mass within the proximal nail matrix, which was excised. Histologic sections of the nail plate showed longitudinal cystic spaces associated with papillary projections of nail matrix epithelium. The parenchyma of the lesion demonstrated bland-appearing spindled cells in a prominent myxoid stroma with abundant mast cells. The spindled cells were focally positive for CD34 and factor XIIIa and negative for S100, pan-cytokeratin, desmin, smooth muscle actin, epithelial membrane antigen, and MART-1. Onychomatricoma (OM) is a rare nail unit biphasic fibroepithelial tumor with multiple radiating digitations lined by papillomatous matrix epithelium. The epithelial component is consisted of matrix cells that generate the thickened nail plate, and the digitations cause characteristic "wormwood" perforations of the nail plate. A fibrous stroma is characteristic with staining positive for CD34 and negative for CD99, epithelial membrane antigen, and S100. This case is unique with the presence of a prominent myxoid stroma associated with the fibrous component of the OM. Only 1 previous report of OM highlights a related finding of a myxocollagenous stroma. This purely myxoid variant represents a new distinct form of OM. Clinicopathologic correlation is essential to avoid confusion with other myxoid tumors such as a superficial acral myxoma, superficial angiomyxoma, or a digital myxoid cyst.
一名57岁女性，左第二趾甲出现增厚、变黄、过度弯曲3年。近端甲皱襞有一个相关结节。从正面观察时，远端甲板有多个圆形穿孔。拔甲后发现近端甲母质内有一个0.7 cm的灰白色肿物，将其切除。甲板的组织学切片显示纵向囊腔与甲母质上皮的乳头状突起相关。病变实质显示在富含肥大细胞的显著黏液样基质中有外观温和的梭形细胞。梭形细胞局部CD34和因子XIIIa阳性，S100、全细胞角蛋白、结蛋白、平滑肌肌动蛋白、上皮膜抗原和MART-1阴性。甲母质瘤（OM）是一种罕见的甲单位双相纤维上皮性肿瘤，有多个由乳头状基质上皮排列的放射状指状突起。上皮成分由产生增厚甲板的基质细胞组成，指状突起导致甲板出现特征性的“蒿状”穿孔。纤维性基质是其特征，CD34染色阳性，CD99、上皮膜抗原和S100染色阴性。该病例独特之处在于存在与OM纤维成分相关的显著黏液样基质。之前仅有1篇关于OM的报道强调了黏液胶原性基质这一相关发现。这种纯黏液样变体代表了一种新的独特的OM形式。临床病理相关性对于避免与其他黏液样肿瘤如浅表性肢端黏液瘤、浅表性血管黏液瘤或指状黏液样囊肿混淆至关重要。
