Loss of basement membranes in the invading front of O-1N, hamster squamous cell carcinoma with high potential of lymph node metastasis: an immunohistochemical study for laminin and type IV collagen.

The change in immunohistochemical localization of the two basement membrane molecules, laminin and type IV collagen, was studied in relation to tumor growth and lymphatic invasion in the transplanted hamster squamous cell carcinoma, O-1N, that has a high potential of lymph node metastasis. At 1 week after transplantation, the tumors consisted of large round-shaped nests of approximately 200 mm in diameter, 80% of which were encircled by continuous laminin and type IV collagen positive lines representing the basement membrane. At 5 weeks, however, the tumor cell nests became half in diameter with invasion in small islands or cords at the periphery and only 40% of them had continuous basement membrane. At 10 weeks, the basement membranes were disrupted in varying degrees in approximately 90% of the tumor cell nests. The disruption was most conspicuous on the outer and invading side of the nests. Lymphatic invasion and lymph node metastasis were observed in animals after 5 weeks of transplantation and the immunoreactivity was absent around tumor cell clusters growing in lymphatic spaces. The findings indicate that the disappearance of basement membrane and reduction in size of tumor cell nests are essential signs for local invasion of tumor cells leading to lymphatic invasion and metastasis to regional lymph nodes.