Primary indeterminate dendritic cell tumor (IDCT) is an extremely neoplastic dendritic cell disorder. Little is known about its pathogenesis, etiology, and prognostic factors because of its rarity. Herein, we present a case report of a skin IDCT that arose in mosquito bite and discuss the correlation between hypersensitivity to mosquito bites and leukemia/lymphoma.A 28-year old man presented with multiple widespread cutaneous plaques and nodules 8 months after being bitten by a mosquito on his back. Dermatological examination revealed multiple skin-colored, well-demarcated plaques and nodules measuring approximately 0.5 to 1.8 cm in diameter all over the body. A biopsy of the skin lesion was taken. Morphologically, the dermis was effaced by round or polygonal cells with oval nuclei and abundant eosinophilic cytoplasm, arranged in nests and in some areas in a sheet-like pattern. The tumor cells were positive for CD68, CD1a, and S-100, whereas negative for Langerin and lack Birbeck granules ultrastructurally. A diagnosis of IDCT was made. No treatment was given. The patient was alive with spontaneous disease regression after 17 months of follow-up.IDCT is an extremely rare disease and may be associated with mosquito bite.