Abstract：
Nevoid melanoma is a subtype of melanoma that histologically resembles a melanocytic nevus. Two subtypes have been proposed for nevoid melanoma, namely papillomatous and maturing. Here, we report the case of a 67-year-old woman who developed two nevoid melanomas on her scalp with composite histological features of papillomatous and maturing subtypes after electrocautery of a nearby solitary scalp papule. The histology of both lesions was very similar, papillary in shape, and both comprised two melanocyte populations, including large atypical melanocytes and small non-atypical melanocytes. Whole-exome sequencing was performed in one of the two lesions, which revealed a high mutation burden (17 mutations/megabase) with co-deletion of CDKN2A. Additional immunohistochemistry revealed that the large and small melanocytes in both lesions were completely negative for p16 and MTAP. A final diagnosis of nevoid melanoma was made. To our knowledge, this is the first report of a nevoid melanoma with both features of papillomatous and maturing subtypes. Pathologists should be aware of this subtype of melanoma to avoid misdiagnosis as a mitotically active melanocytic nevus. In this case, immunohistochemistry for p16 and MTAP, in addition to molecular analysis, helped in the final diagnosis.
摘要：
痣样黑色素瘤是黑色素瘤的一种亚型，在组织学上类似于黑素细胞痣。已经提出了两种亚型用于痣性黑色素瘤，即乳头状瘤和成熟。这里,我们报告了一例67岁的女性，她的头皮上出现了两个结节状黑色素瘤，在附近的孤立头皮丘疹电烧灼后，其具有乳头状瘤和成熟亚型的复合组织学特征。两个病变的组织学非常相似，乳头状形状，两者都包含两个黑素细胞群，包括大型非典型黑素细胞和小型非非典型黑素细胞。在两个病变之一中进行了全外显子组测序，这揭示了高突变负担(17个突变/兆碱基)与CDKN2A的共缺失。另外的免疫组织化学显示，两个病变中的大黑素细胞和小黑素细胞对p16和MTAP完全阴性。做出痣样黑色素瘤的最终诊断。据我们所知,这是首次报道具有乳头状瘤和成熟亚型特征的结节样黑色素瘤。病理学家应该意识到黑色素瘤的这种亚型，以避免误诊为有丝分裂活跃的黑素细胞痣。在这种情况下,p16和MTAP的免疫组织化学，除了分子分析，帮助最终诊断。
