lymphadenopathy in the left infraparotid area, which progressed to clinical stage Ⅲ. In addition, the lesion size was 1.4×1 cm 2 at diagnosis, and it increased to 2.0×2.5 cm 2 after 3 weeks and to 3.0×2.3 cm 2 in permanent biopsy. In general, MCC is well known to grow fast in about two-third and slow in one-fourth, but this case is meaningful in that it shows how rapidly growing MCC is. According to a previous study, the false-negative rate of sentinel lymph node biopsy in MCC patients is reported to be about 17.1%. Thus, it is thought that in MCC patients with rapidly growing lesions, neck dissection may be considered even when the tumor is diagnosed as stage I. 10 We had a rapidly growing MCC and treat successfully with wide excision of the MCC, neck lymph node dissection, reconstruction using RFFF, and subsequent radiotherapy. Through this case report, we would like to talk about the treatment experience of the rapidly growing MCC and fast multidisciplinary cooperation is very helpful for the appropriate treatment of the rapidly growing MCC.