Table 4.

Grading Scheme for Invasive Pulmonary Adenocarcinomas

Grade	Differentiation	Patterns
1	Well-differentiated	Lepidic predominant with no or less than 20% of high-grade patterns
2	Moderately differentiated	Acinar or papillary predominant with no or less than 20% of high-grade patterns
3	Poorly differentiated	Any tumor with 20% or more of high-grade patterns

The model is based on the predominant histologic plus high-grade patterns. The latter includes solid, micropapillary, and complex glandular patterns.