Grading is related to cell type and morphology, degree of differentiation, and tumor architecture. Cell type is typically a keratinizing large cell, characterized by pearl formation. The nuclei have dispersed chromatin and occasional nucleoli. Mitotic activity is infrequent. Cell type is usually a non-keratinizing large cell, with absent pearl formation.
Mitotic activity is increased.
Cell type is commonly a small cell. The cells have basophilic cytoplasm with high nuclear to cytoplasmic ratios. Cell and nuclear size are uniform. Mitotic activity is abundant, and abnormal mitoses are present. The tumors are typically infiltrative, with individual malignant cells at the borders.