A hypothesis of a common carcinogenic influence on the 2 separate precursor cells has been suggested.[47–49] Koba et al reported combined MCC as a collision tumor comprising a rare MCC variant with CK20 negative and CD56/TTF-1 positive immunostaining.[48] Suaiti et al presented a case of combined MCC in the left ear, in which both tumor components metastasized to the same lymph node of the parotid during immunosuppression.[49] This combined MCC is considered a fortuitous collision between the MCC and SCC. This evidence concerns the gene KRT20 and Merkel cell skin cancer.