Purpose: The growth pattern of peripheral squamous cell carcinoma (SCC) of the lung is divided into two types: alveolar space-filling (ASF) growth and alveolar space-destructive (ASD) growth. The aim of this study was to investigate the clinicopathological differences between cancer cells displaying ASF and ASD growth.
Methods: We analyzed 155 patients with peripheral SCC measuring 30 mm or less in diameter. The proportion of ASF in the total tumor area (%ASF) was determined using digital image analysis. We examined the clinicopathological characteristics of the cancer cells and compared the immunophenotypes of high %ASF tumors (> 30%) and low %ASF tumors (0%). Finally, we analyzed the prognostic impact of ASD area with small SCC cases (≤ 2.0 cm, n = 72).
Results: Cases of high %ASF tumors showed significantly lower frequencies of lymphovascular invasion (p = 0.008). Immunohistochemical staining revealed that the expression score of laminin-5, invasive-related molecule, in cancer cells was significantly lower in high %ASF cases than in low %ASF cases (p = 0.001). Within the same tumor, laminin-5 expression in the ASF area was significantly lower than that in the ASD area (p = 0.001). The overall 5-year survival rate of patients with a larger ASD area (> 1.0 cm2) was significantly lower than that of patients with a smaller ASD area (≤ 1.0 cm2) (p = 0.017).
Conclusions: In this study, we clearly showed that cancer cells presenting with ASF represents a "less invasive phenotype" in peripheral SCC.
Keywords: Alveolar space destructive (ASD); Alveolar space filling (ASF); Peripheral lung cancer; Squamous cell carcinoma.