An Immunohistochemical Study of the Apocrine Type of Cutaneous Mixed Tumors with Special Reference to Their Follicular and Sebaceous Differentiation

The study conducted an immunohistochemical analysis on 8 cases of apocrine type cutaneous mixed tumors, revealing that 7 cases exhibited follicular and/or sebaceous differentiation. Various markers such as carcinoembryonic antigen (CEA), epithelial membrane antigen, and gross cystic disease fluid protein‐15 were identified in the tubular structures, while S‐100 protein and vimentin were found in solid nests and stromal cells. The study observed diverse keratin expression patterns, with CK7, CK8/18, and CK19 consistently present in the inner cells of tubular structures. The findings suggested that these tumors can exhibit immunophenotypical patterns similar to those of hair follicles, sebaceous glands, and apocrine glands, indicating a resemblance to the folliculosebaceous‐apocrine unit.