Immunohistochemical and immunoelectron microscopical localization of procollagen III peptide in papillary carcinoma of thyroid.

The immunohistochemical localization of procollagen III peptide, a precursor of type III collagen, was examined in 38 papillary carcinomas and 25 follicular neoplasms using an immu-noperoxidase technique. Although localization of procollagen ill peptide was not demonstrated in normal follicular cells, distinct cytoplasmic immunostaining of neoplastic cells was frequently found in the tissues examined, as were stromal fibroblasts. Such cytoplasmic immunostaining was observed in 92.1 % of 38 papillary carcinomas and in 36.0% of 25 follicular neoplasms. Cytoplasmic immunoreactivity in papillary carcinomas was more intense at the peripheral zone of the tumor and correlated with the degree of invasiveness. The controls, in which the primary antibody was preabsorbed with procollagen ill peptide or replaced with normal rabbit serum, showed only faint background staining in all specimens. Immunoelectron microscopical examination revealed that electron-dense deposits, indicating procollagen III peptide, were located in the perinuclear space, Golgi apparatus, and rough endoplasmic reticulum of papillary carcinoma cells. These results suggest that neoplastic cells, especially papillary carcinoma cells, could play an important role in type III collagen production, possibly in connection with the creation of an environment that is conducive to their progression.