Abstract：
UNASSIGNED: Melanocytic matricoma with atypical features is a rare, biphasic adnexal neoplasm displaying hair matrix differentiation, with only 3 reported cases worldwide. Generally, the lesion comprised a solid matrical and supramatrical cell proliferation, admixed with intermediate cell aggregates with sparse anucleated \"shadow cells\" and a prominent pigmented melanocytic hyperplasia. We report the case of a 78-year-old man with a slow-growing crusted lesion on the frontal left scalp, which in a matter of 1-2 months became a 0.6 cm well-defined, black purplish exophytic nodule. Histopathologically, the lesion presented a well-circumscribed border with a nodular dermal growth pattern, presenting different architectural features varying from benign pilomatricoma-like changes to atypical features such as moderate-to-high nuclear pleomorphism in both basaloid (matrical/supramatrical) and epidermal (keratinous) components. Strong nuclear and cytoplasmic positivity for β-catenin was observed in matrical cells, whereas prominent cytoplasmic membrane positivity for Melan-A in dendritic melanocytes. Owing to the evidence of atypical cytological features, we propose the \"atypical/borderline\" category of melanocytic matricoma as part of a possible spectrum among matrical neoplasms. Pathologists should be aware of any atypical histopathological features while reporting cases due to their potential malignant transformation.
摘要：
■具有非典型特征的黑色素细胞瘤是一种罕见的，显示毛发基质分化的双相附件肿瘤，全球只有3例报告病例。一般来说,病变包括实体基质和基质上细胞增殖，与中间细胞聚集体混合，稀疏的无核“阴影细胞”和明显的色素黑素细胞增生。我们报告了一个78岁的男性，他的左前头皮上有一个缓慢增长的结痂病变，在1-2个月的时间里，它变成了一个0.6厘米的界限，黑色紫色外生结节。组织病理学,病变呈现界限分明的边界，具有结节性真皮生长模式，表现出不同的建筑特征，从良性毛囊瘤样变化到非典型特征，例如基底细胞（基质/上基质）和表皮（角质）成分的中至高核多态性。在基质细胞中观察到β-连环蛋白的强细胞核和细胞质阳性，而树突状黑素细胞中Melan-A的细胞质膜阳性。由于非典型细胞学特征的证据，我们建议将黑色素细胞基质瘤的“非典型/边界线”类别作为基质肿瘤中可能的频谱的一部分。病理学家应了解任何非典型的组织病理学特征，同时报告由于其潜在的恶性转化的病例。
