The diagnosis of malignant melanoma presents a clinical challenge and relies principally on histopathological evaluation. Previous studies have indicated that increased expression of the DEK oncogene, a chromatin-bound factor, could contribute to the development of melanoma and may be a frequent event in melanoma progression. Here, we investigated DEK expression by immunohistochemistry in a total of 147 melanocytic lesions, including ordinary nevi, dysplastic nevi, Spitz nevi, melanoma in situ, primary invasive melanomas, and metastatic melanomas. Most benign nevi (ordinary, dysplastic, and Spitz nevi) were negative or exhibited weak staining for DEK, with only 4 of 49 cases showing strong staining. Similar to benign nevi, melanoma in situ also demonstrated low levels of DEK expression. In contrast, the expression of DEK in primary invasive melanomas was significantly higher than benign nevi (P < .0001). Moreover, DEK expression was significantly increased in deep melanomas (Breslow depth >1 mm) and metastatic melanomas as compared with superficial melanomas (Breslow depth ≤1 mm) (P < .05). Our findings indicate that DEK overexpression may be a frequent event in invasive melanomas, and further augmentation of DEK expression may be associated with the acquisition of ominous features such as deep dermal invasion and metastasis. These data suggest a role of DEK in melanoma progression.