Expression of laminin in thyroid gland and thyroid tumors: an immunohistologic study.

Thirty-five thyroid tumors and four normal thyroids were immunohistochemically investigated for the presence of laminin, a major basement membrane component. The thyroid follicles in normal tissues and in nodular goiters were surrounded by a continuous rim of laminin positivity, as were also the papillae of papillary carcinomas. Follicular adenomas and well-differentiated follicular carcinomas also showed laminin positivity around most of the follicles. Anaplastic thyroid carcinoma lacking a distinct compartmentalization of tumor cells also lacked pericellular laminin. However, in contrast to all other thyroid tumors, an intense laminin positivity was found in scattered tumor cells of anaplastic carcinomas. Laminin positivity is thus a feature reflecting the differentiation level of thyroid tumors, but, unlike most other carcinomas, differentiated thyroid tumors have basal laminae surrounding the differentiated structural units.