Figure 4

Pathologically diagnosed adrenal pheochromocytoma (HE × 400) shows a wide variety of tissue structure and cell morphology. Tumor tissue is separated into lobulated parts by fibrous bands come from envelope. Tumor cells (most are polygonal, few are fusiform and prismatical) are mostly arranged in cords, nests, and pieces, which are separated by thin-walled blood sinuses and fibrous tissues rich in blood vessels. Tumor cells show unclear boundaries and have lots of cytoplasm as well as inhomogeneous particles (slightly basophilic or amphophilic). Tumor cell nucleus is round or oval, which has obvious nucleolus and little karyokinesis.