Recommendations for Staging When the Rules Don't Fit
A large number of factors may influence survival in patients with lung cancer and it would be impossible to design a workable staging system that accounted for all of them. In practice, we can only use a classification that discriminates the majority of patients within a definable subgroup. This imposes limitations on the definitions and, unless such limitations are accepted, we would become involved in a hopelessly complex and unmanageable number of subcategories.

In the absence of a body of data that describes the prognostic implications of tumors with no applicable specific staging rule, the TNM and stage classifications must be assigned according to logic or convention. With these points in mind the following illustrations of common questions and problems in staging lung cancer are presented.

Discontinuous Tumor Foci in Visceral or Parietal Pleura
Tumor foci in the parietal or visceral pleura that are discontinuous from direct pleural invasion by the primary tumor should be staged T4. Discontinuous tumor lesions outside the parietal pleura in the chest wall or in the diaphragm are classified M1.

Invasion of the Phrenic Nerve
Invasion of the phrenic nerve is apparent clinically and usually represents limited direct extension of the primary tumor. As such, it indicates T3 disease and does not preclude surgical treatment, if no criteria for T4 pertain.