Peripheral squamous cell carcinoma of lung: patterns of growth with particular focus on airspace filling.

Because the clinical behavior of low-stage adenocarcinomas of the lung is best predicted when adjusted for the presence of a lepidic growth pattern, we studied the marginal growth patterns of 62 peripheral squamous cell carcinomas of lung focusing on the patterns of marginal/peripheral growth and presence of an alveolar filling component. Approximately one fourth of squamous carcinomas had 20% of their gross diameters composed of carcinoma cells filling airspaces with preserved alveolar architecture, and 26% of these cases had their gross size downgraded from a T2 to a T1 lesion. Despite this size recalculation, insufficient numbers of cases made it impossible to determine if this change had independent prognostic significance for T1/T2N0 lesions. Nonetheless, such a growth pattern was common and should be studied further in larger series to determine if an airspace filling growth pattern in squamous carcinoma is clinically important.