Distribution of basement membrane in squamous cell carcinoma of the head and neck.

The immunohistologic distribution of the basement membrane components, type IV collagen and laminin, was evaluated in 57 alcohol-fixed, paraffin-embedded tissue sections which demonstrated immunostaining patterns with antigen preservation similar to that of frozen tissue sections. Normal and hyperplastic squamous mucosa, a spectrum of intraepithelial neoplasia, and invasive squamous cell carcinomas of the upper aerodigestive tract were evaluated by this technique. Prominent and continuous basement membrane staining characterized normal and reactive hyperplastic squamous mucosa. The basement membrane varied greatly with epithelial dysplasia and was usually prominent and continuous in mild to moderate dysplasias. In severe dysplasia/carcinoma in situ, the basement membrane was often thinned and occasionally discontinuous. The distribution of basement membrane in invasive carcinomas was also varied. Basement membrane was usually present in invasive tumors with well-defined tumor host borders and cohesive patterns of stromal invasion which were interpreted as foci of histologic differentiation. In contrast, invasive carcinomas with irregular cords or single tumor cells distributed through the host stroma invariably lacked basement membrane at the tumor-stromal interface; this was interpreted as a decreased expression of histologic differentiation. We conclude that 1) severe intraepithelial neoplasia is often associated with irregularities of basement membrane and that the absence of basement membrane does not necessarily define invasive cancer; 2) immunolocalization of basement membrane in invasive carcinomas is common in areas displaying histologic differentiation; and 3) the association of basement membrane distribution and histologic pattern of tumor invasion suggests that squamous cell carcinomas are capable of undergoing focal histologic differentiation after invasion has occurred.