The molecular background of a significant proportion of spitzoid neoplasms is still unknown. Recently, activating mutations in MAP2K1 have been described in a few spitzoid lesions, but not in benign Spitz nevi. We report four cases of melanocytic tumors with spitzoid features in which a MAP2K1 mutation was detected. The lesions did not show a single distinct phenotype and ranged from benign to malignant. Two cases resembled desmoplastic Spitz nevi. Based on the combination of morphological, immunohistochemical, and molecular findings, one case was classified as benign, one as probably benign, possibly intermediate low-grade (MELTUMP—melanocytic tumor of unknown malignant potential), one case was classified as intermediate (MELTUMP), and one case was considered a superficial spreading melanoma with spitzoid features. Based on this, we conclude that MAP2K1 mutations can indicate a spitzoid genetic signature and can be found in both benign and malignant spitzoid neoplasms.

大部分 spitzoid 肿瘤的分子背景仍然未知。最近，在一些 spitzoid 病变中描述了MAP2K1 中的激活突变，但在良性 Spitz 痣中没有描述。我们报告了四例具有 spitzoid 特征的黑素细胞肿瘤，其中MAP2K1检测到突变。病变没有表现出单一的不同表型，范围从良性到恶性。两个病例类似于促纤维增生性 Spitz 痣。结合形态学、免疫组化和分子学检查结果，1例为良性，1例为可能良性，可能为中低度（MELTUMP——恶性潜能未知的黑色素细胞瘤），1例为中度（MELTUMP） ，并且有一个病例被认为是具有 spitzoid 特征的浅表扩散性黑色素瘤。基于此，我们得出结论，MAP2K1突变可以表明 spitzoid 遗传特征，并且可以在良性和恶性 spitzoid 肿瘤中找到。