Scarring in papillary carcinoma of the thyroid: report of two new cases with exuberant nodular fasciitis-like stroma

Aims: To describe two new cases of papillary carcinoma of the thyroid with exuberant nodular fasciitis-like stroma, one of which was characterized by previously unreported transformation into a poorly differentiated lesion. M oreover, we explore the presence of TGF-beta to help to clarify the pathoge nesis of the collagen formation. Methods and results: The case characterized by an aggressive behaviour exhi bited areas of transformation into a poorly differentiated (insular) carcin oma of the thyroid. In both cases, as revealed by immunohistochemistry, neo plastic cells produced and secreted high amounts of TGF-beta. On the contra ry, TGF-beta immunoreaction was never present in the normal thyroid or in p apillary carcinomas without collagen bundles, while a weak, exclusively int racellular reaction was present in a patchy manner in cases showing intratu moral fibrous bundles. Conclusions: The rare variant of papillary thyroid carcinoma characterized by exuberant stroma may give rise to more aggressive lesions, as do other h istotypes of differentiated thyroid carcinomas. TGF-beta, the fundamental c ytokine which mediates scarring and activation of myofibroblasts, most prob ably induces the exuberant stroma.