Analysis of KIT expression and gene mutation in human acral melanoma: with a comparison between primary tumors and corresponding metastases/recurrences.

KIT mutations play an important role during the pathogenesis of melanoma. Acral melanoma, which is the most common type in China, is more likely to harbor activating KIT mutations. Currently, there are few large studies on KIT expression and mutation in acral melanoma, especially in patients with matched primary/secondary pairs. Here, we investigated KIT expression and mutation in 39 primary acral melanomas together with their corresponding secondary tumors (17 lymph node metastases, 6 local recurrences, and 3 skin metastases) and explored the relationship between KIT expression, mutation, and clinicopathologic characteristics. Cytoplasmic and membranous staining for KIT was noted in 17 cases (43.6%) of 39 primary acral melanomas. KIT expression in patients without lymph node metastases at presentation was significantly higher than those with lymph node metastases (P = .024). KIT mutations were detected in 9 (23.1%) of 39 cases of primary acral melanomas. KIT expression did not correlate with KIT mutation status. In 23 cases with primary/secondary pairs, KIT mutations were observed in 6 cases. Comparison of KIT mutations between primary and secondary tumors showed a discordance rate of 13.0% (3/23). We concluded that KIT mutations are common in acral melanoma, and patients with acral melanoma should be screened for KIT mutations. Mutation status may change during metastases/recurrences after diagnosis of primary tumors. This has important clinical implications, and its mechanism needs further investigation.