Immunohistochemical expression of type VI collagen in superficial fibromatoses

The expression o f type VI collagen was studied immunohistochemically in 26 cases o f superficial fibromatoses (palmar, plantar and penile) using an immuno peroxidase method for light microscopic visualization. The polyclonal antibody against type VI collagen used in this study was isolated from human placenta and its s peci f ity was tested by immunoblotting assay. All cases consistedofmultiple nodulesshowinga variable degree ofcellularity and fibrosis. Depending on the predominant histological appearance of these nodules, each case was assigned to the three following phases: proliferative, involutional and residual. Morphologically normal palmar and plantar aponeuroses were included as controls Immunohistochemical findings showed that type VI collagen was present as longitudinal thin fibers in normal palmarand plantaraponeuroses. A differentialexpression of this collagen was ound in the different stages of superficial fibromatoses. Type VI collagen was markedly expressedas a distinct fibrillar network in the extracellular matrix (ECM) surrounding proliferating stromal cells in proliferative and involutional phases. Its expression completely disappeared from the connective tissue undergoing fibrotic transformation during involutional and residual phases. The results of the present study suggest that type VI collagen is an extracellular marker of stromal tissue proliferation and is involved in the early phases of tissue remodelling occurring in the superficial fibromatoses.