唾液腺多形性腺腫の軟骨様組織におけるタイプＩ，ＩＩおよびＸコラーゲンの局在

Abstract

Pleomorphic adenoma most commonly occurs in salivary gland tumors. Its morphological features are diverse, and in typical cases myxomatous, cartilaginous, and even osseous tissue are seen in the stroma. It has been reported that the cartilaginous tissue is derived from the myxomatous tissue. Furthermore, the stromal cells are thought to derive from neoplastic myoepithelial cells. However, the histogenesis and morphological features of the cartilaginous tissue have not been fully clarified. We studied the histogenesis of the cartilaginous tissue and histological differences from hyaline cartilage by assessing the localization of Type I, II, and X collagens. Seven cases of pleomorphic adenoma with the cartilaginous tissue in their stroma were examined both histopathologically and immunohistochemically.Histopathological examination revealed that the cartilaginous tissue consisted of both myxomatous and cartilaginous regions and that the cell lineage in the cartilaginous tissue was basically similar to that of hyaline cartilage: small round-shaped chondrocytic cells were found in the peripheral portion of the cartilaginous region, and swollen cells with condensed nuclei similar to hypertrophic chondrocytes were present mainly in the central portion. However, alizarin red staining was occasionally positive in the cartilaginous tissue, suggesting that calcification might be rather sparse in the cartilaginous tissue of pleomorphic adenoma.Type I collagen was mainly localized in spindle-shaped cells in the myxomatous region surrounding the cartilaginous region. It was also weakly expressed in chondrocytic cells. Conversely, type II collagen was strongly expressed in chondrocytic cells, while it was weakly expressed in spindle-shaped cells in the myxomatous region. Type X collagen was weakly expressed in chondrocytic cells that showed evidence of hypertrophy. The distribution of each collagen was sparse in the extracellular matrix.These results suggest that cell differentiation in the cartilaginous tissue of pleomorphic adenoma is fundamentally similar to that of hyaline cartilage except for low expression of these collagen species in the extracellular matrix. It may explain the low calcification in the cartilaginous tissue of pleomorphic adenoma.