Abstract：
UNASSIGNED: Melanocytic matricoma is a rare benign pilar tumor characterized by matrical differentiation and interspersed dendritic melanocytes. It may show cellular atypia and brisk mitotic activity. Histological characterization of some lesions may be difficult. In addition, because the reported cases are few and have limited follow-up, there is insufficient experience to define outcome-based criteria for malignancy. Some cases of melanocytic matricoma with more prominent atypia have been reported as malignant, but their clinical behavior is uncertain. We present a melanocytic matricoma with interspersed benign dendritic melanocytes, but moderate basaloid atypia, focally brisk mitotic activity, and atypical mitoses. Despite the apparently good delimitation of this tumor, higher magnification revealed a slightly irregular border. However, overt malignant features such as necrosis, frank asymmetry, deep infiltration, and ulceration were not present. This tumor showed a complex aberrant genomic profile with multiple whole chromosomes or chromosomal arms, losses, and duplications. The tumor mutational burden was high. A loss-of-function alteration in CDKN2A and a loss-of-function mutation in TP53 were also present. This unexpected molecular profile contrasts with the relatively bland histology of the tumor and is in line with the difficulties in microscopic differential diagnosis between melanocytic matricoma and an indolent malignant pilomatrical tumor. We suggest that molecular studies and longer follow-up periods may help to further understand and more precisely categorize borderline pilomatrical tumors with melanocytic hyperplasia.
摘要：
■黑色素细胞瘤是一种罕见的良性毛囊肿瘤，其特征是基质分化和散布的树突状黑色素细胞。它可能显示细胞异型性和活跃的有丝分裂活性。某些病变的组织学表征可能很困难。此外,因为报告的病例很少，随访有限，没有足够的经验来定义基于结果的恶性肿瘤标准.一些具有更突出的异型性的黑色素细胞瘤病例被报道为恶性，但是他们的临床行为是不确定的。我们提出了一个黑素细胞瘤与散布良性树突黑素细胞，但是中度基底细胞异型，局灶性有丝分裂活跃，和非典型有丝分裂。尽管这个肿瘤的界限看起来很好，更高的放大倍数显示边界略微不规则。然而,明显的恶性特征，如坏死，弗兰克不对称，深层渗透,溃疡不存在。该肿瘤显示出复杂的异常基因组图谱，具有多个完整染色体或染色体臂，损失,和重复。肿瘤突变负担很高。还存在CDKN2A中的功能丧失改变和TP53中的功能丧失突变。这种出乎意料的分子谱与肿瘤的相对平淡的组织学形成对比，并且与黑素细胞基质瘤和惰性恶性毛发肿瘤之间的显微镜鉴别诊断困难一致。我们建议，分子研究和更长的随访时间可能有助于进一步了解和更准确地分类具有黑素细胞增生的边缘毛管瘤。
