Immunolocalization and distribution patterns of type IV collagen alpha chains in oral mucosal melanoma

The basement membrane (BM) is mainly composed of type IV collagen, which is composed of triple combinations of six distinct alpha (α) chains in a tissue-specific manner. The six collagen chain-specific antibodies (α1-α6) were used to examine the BMs of the oral epithelium (OE) and tumor clusters in oral mucosal melanoma (OMM). Eight OMM cases were examined. Results showed that the α1 and α2 chains were constantly detected at the BM of the normal OE as well as at the OE with atypical melanocytic proliferation and in invasive melanoma with nodular nests. The α1 and α2 chains were intermittently detected in in situ OMM, early invasive OMM and advanced invasive OMM with sheet-like nests. Gradual loss of α5 and α6 from the OE with atypical melanocyte through in situ OMM and early invasive OMM was observed. These findings suggest that changes in the immunolocalization and distribution patterns of type IV collagen α chains are associated with the progression of OMM. The distribution pattern of type IV collagen α chain varies depending on the architecture of the nest.