Immunohistochemical study of thrombospondin and its receptors alpha root beta 3 and CD36 in normal thyroid and in thyroid tumours

Aim-To describe the pattern of distribution of thrombospondin (TSP1) and it s receptors, alpha root beta 3 integrin and CD36, in normal human thyroid t issue and to compare their expression in different benign and malignant thy roid conditions. Methods-Immunohistochemistry was used to study TSP1 and its receptors in 40 surgical thyroidectomy specimens (normal parenchyma, 7; follicular adenoma , 4; multinodular goitre, 13; papillary carcinoma, 6; follicular carcinoma, 8; anaplastic carcinoma, 2). Results-In the normal thyroid parenchyma, there was weak expression of TSP1 limited to the vessels with no staining of the extracellular matrix. In go itres, the expression of TSP1 was more pronounced in areas of fibrosis, wit h staining of alpha root beta 3 on thyrocytes located in the vicinity. In t hyroid adenomas, expression of TSP1 was slightly enhanced compared with nor mal tissue, located in the basement membrane of vessels. In papillary carci nomas, TSP1 was abundant in the desmoplastic stroma with a cytoplasmic dist ribution of alpha root beta 3 integrin in thyrocytes. In follicular carcino mas, TSP1 was less abundant in the extracellular matrix, limited to the ves sels of the stroma with a weaker expression of alpha root beta 3 on thyrocy tes than in papillary carcinomas. In anaplastic carcinomas, TSP1 was only p resent in the numerous capillaries of the stroma, with a marked positivity for alpha root beta 3 in one case. No immunostaining of thyrocytes is obser ved with CD36. Conclusions-These results suggest the importance of the interaction between alpha root beta 3 integrin and TSP1 during remodelling of the matrix in fi brous goitres with areas of early sclerosis comparable with wound healing. In papillary carcinomas, the overexpression of TSP1 restricted to the strom a suggests protective effects against tumour progression.