Papillary thyroid cancer stroma - histological and immunohistochemical study.

Abstract

Thyroid cancer is the most frequent endocrine neoplasia. The incidence of the disease has been increasing in the past few decades in many regions, especially where the population was subject to some forms of accidental exposure. Among all the histopathological forms, papillary thyroid cancer (PTC) is the most common histological subtype of malignant thyroid tumor, representing about 80-90% of all malignant thyroid tumors. Although it is generally accepted that tumor stroma plays an essential role in the development and metastasis of tumor cells, histopathological studies focused on tumor cells characteristics. In this study, we evaluated the characteristics of tumor stroma histopathologically and immunohistochemically examining a total of 18 cases of papillary thyroid carcinomas, of which 18 cases were classic papillary carcinomas, 11 cases papillary carcinomas, follicular forms, five cases were papillary carcinomas - formed with tall-cells, three cases of papillary carcinomas, solid variants and one case was interpreted as an oncocytic variant. Most papillary carcinomas have been typically characterized by the presence of neoplastic papillae, composed of a central axis of fibro-vascular, branched, and coated by one or more layers of cubic or prismatic epithelial cells. In three typical papillary carcinomas, the stroma was composed of coarse connective axes rich in collagen fibers. The predominantly fibrous stroma, consisting of connective septum was observed in four cases, while in one case of papillary carcinoma, solid variant, we have identified a hyaline stroma; in one case was revealed a myxoid stroma. Diffuse stromal calcifications have been identified in two cases only. In the tumoral stroma, there were identified inflammatory infiltrates in nine cases, formed mostly of lymphocytes, and in one case, there was observed the presence of aggregated lymphoid nodules. The immunostaining with anti-CD34 antibody showed that in papillary thyroid carcinomas there is a well-represented vascularity, mostly made of small vessels (arterioles, venules, capillaries) with diameters between 7 and 50 μm, and immunostaining with anti-vimentin and anti-α-SMA antibody showed an increased number of fibroblasts, respectively myofibroblasts in the tumoral stroma. We believe that in the same thyroid tumor there are several clones of neoplastic cells that reshape the stroma, giving it certain histopathological characteristics.