Clear cell hidradenoma was found to be composed of two main types of cells: (1) a fusiform, dense cell located at the periphery of the tumor strands contained a large number of tonofilaments and a small amount of glycogen; and (2) a large and "clear" cell, differentiated from the former toward the center of the tumor strands, was filled with glycogen but poor in tonofilaments. Ail tumor cells were positive for enzymes present in normal eccrine glands in a higher concentration than in normal apocrine glands. The luminal spaces were lined by one of four types of epithelium, ie, embryonic epidermal, dermal, transitional, or secretory. Some tubular lumina were found to be very similar to the unopened secretory coil of immature embryonic eccrine gland. The majority of the clear cell tumors of the skin represent an immature eccrine sweat gland tumor.
Ken Hashimoto, Richard J. DiBella, Walter F. Lever. Clear Cell HidradenomaHistological, Histochemical, and Electron Microscopic Studies. Arch Dermatol. 1967;96(1):18–38. doi:10.1001/archderm.1967.01610010024003