Differential expression of alpha1 (IV) and alpha5 (IV) collagen chains in basal-cell carcinoma

BACKGROUND: Basement membrane alterations are common in malignancies, and they may indicate tumoral aggressiveness. Distinct patterns of tumoral coverage by collagen IV were reported in nodular and aggressive basal-cell carcinomas (BCCs). Differential expressions of alpha (IV) collagen chains were also shown on frozen sections. The aim of our work was to document the immunohistochemical expression of alpha1, alpha3, and alpha5 (IV) collagen chains in BCC after routine fixation and processing. METHODS: The patterns of distribution of alpha1 (IV), alpha3 (IV), and alpha5 (IV) collagen chains were studied in 20 formalin-fixed and paraffin-embedded BCCs showing different infiltrative patterns. One trichoblastoma was used as control. RESULTS: In nodular BCCs, the expression of alpha5 (IV) collagen chain was downregulated and uneven. By contrast, alpha1 (IV) collagen chain expression was preserved around these tumors similar to the surrounding skin. However, the alpha1 (IV) collagen chain expression was discontinuous or absent in BCC areas showing an infiltrative pattern of extension. The alpha3 chain was absent both underneath all BCCs and non-neoplastic skin. CONCLUSIONS: The basement membrane alterations around nodular BCCs involved more precisely the alpha5 (IV) collagen chains. Defects in alpha1 (IV) collagen chain expression seemed to be associated with a tumoral invasive and infiltrative pattern. The biological significance of these findings is unclear.