X-Cell Morphology in the Epidermal Papillomas of Flatfish Collected from Coastal Waters of Hokkaido, Japan

Abstract

Skin tumors of five species of flatfish, Platichthys stellatus, Cleisthenes pinetorum herzensteini, Hippoglossoides dubius, Kareius bicoloratus and Limanda schrenki collected from the coastal waters of Hokkaido Island, Japan, are diagnosed as epidermal papillomas. These epidermal papillomas have characteristic X-cells in the lesions. The X-cells have a large nucleolus in the nucleus, the cell membrane is clearly visible and rather smooth, and the cytoplasm is granular and contains many vacuoles. Both nucleoplasm and cytoplasm are weakly basophilic. The X-cells in the dermis are smaller than those in the epidermis. The latter cells were first recognized at 4-5μm in size in the basal layer and appeared to degenerate in the final stages beyond the 20 μm size. These characteri-stic cells were common to all the species observed and may originate from small wandering cells 2-3μm in size.