The immunophenotypic features of the cases in this study are summarized as follows: (1) the neoplastic cells of all cases expressed one or more plasma cell associated antigens; and CD138 and CD38 were better than PC in both sensitivity and specificity as well; (2) some difference of immunophenotypic expression in EMP, SPB and inflammation of sinonasal regions with numerous PC infiltrations were observed; (3) 87.5% of the cases displayed Ig light chain restriction, with Igλ type predominant; (4) Ki-67 index was elevated with the advanced histologic grading. Here, MKI67 is linked to pachyonychia congenita.