The undifferentiated subtype, which is more common, is characterized by large tumour cells with a syncytial appearance, round to oval vesicular nuclei, and large central nucleoli. The nuclei can be chromatin-rich rather than vesicular and the neoplastic cells generally have scant amphophilic or eosinophilic cytoplasm. The malignant cells can assume spindle-cell features in fascicular arrangements.
The differentiated subtype exhibits cellular stratification and pavementing, often with plexiform growth; occasional keratinized cells may be present. Compared with those in the undifferentiated subtype, the neoplastic cells are often slightly smaller, the N: C ratio is lower, the nuclei are often more chromatin-rich and the nucleoli are usually less prominent, Focally, intercellular bridges may be present.
已分化的亚型表现出细胞分层和膜状生长，通常呈丛状生长，偶尔可见角化细胞。与未分化亚型相比，肿瘤细胞通常较小，n: c 比值较低，细胞核染色质丰富，核仁不明显，局灶性、细胞间桥梁可能存在。