3MCA-induced tumor in Spalax . (A) Light microscopic examination. Note spindle, epithelioid and giant multinuclear cells (empty arrow); nuclei are variable in shape, size and chromatin distribution; nucleoli vary in frequency. Hematoxylin and eosin staining, ×100. (B) Transmission electron microscopy (TEM): dilated, elongated rough endoplasmic reticulum (black arrows) and abundant collagen fibers (white arrows) (C) TEM: a giant, monstrous nucleus (N). (D) Cell line established from Spalax tumor, phase contrast image after six months of continuous cultivation (×200). 3MCA, 3-Methylcholantrene.