Verification of the newly proposed T category (seventh edition of the tumor, node, and metastasis classification) from a clinicopathological viewpoint in non-small cell lung cancer-special reference to tumor size.

Background: This study first verified the T classification, which is the major point of the revision regarding the seventh Tumor, Node, and Metastasis classification, from a viewpoint of the clinicopathological findings at the primary tumor site in non-small cell lung cancer.

Methods: The medical records of 1393 patients with non-small cell lung cancer who underwent a complete resection at this hospital from 1974 to 2003 were thoroughly reviewed for pathologic findings and survival.

Results: According to greatest dimension of the primary tumors, the 5-year postoperative survival was 77.8% for T1a (< or =2 cm), 63.3% for T1b (< or =3 cm), 46.4% for T2a (< or =5 cm), 38.8% for T2b (<7 cm), and 21.4% for T3 (>7 cm). The differences among those new T categories were all statistically significant. The incidence of lymphatic permeation within the primary tumor was 17.2% for T1b and 29.8% for T2a (T1b versus T2a, p < 0.05). The incidence of vascular invasion within the primary tumor was 24.9% for T1b, 35.3% for T2a, and 54.2% for T2b (T1b versus T2a and T2a versus T2b, p < 0.05). On the other hand, the incidence of pleural invasion of the primary tumor was 18.1% for T1a, 29.4% for T1b, 49.3% for T2a, 47.3% for T2b, and 87.5% for T3 (T1a versus T1b, T1b versus T2a, T2b versus T3, p < 0.05). Significant differences were observed among the newly revised T subsets in at least one incidence of lymphatic, vascular, or pleural invasion.

Conclusions: The new T classification, which is based mainly on the tumor size, is therefore considered to be appropriate for the pathologic findings of the primary tumor.