[Immunohistochemical study of borderline thyroid lesions with special reference to relationships among nuclear features, type IV collagen and malignancy of follicular lesions].

It is very difficult to differentiate follicular adenoma from follicular carcinoma in thyroid follicular lesions. The authors investigated the biological behavior of these thyroid follicular lesions using immunohistochemical techniques. Specimens taken from normal thyroid, 2 cases; follicular adenoma, 9; atypical adenoma, 7; and follicular carcinoma, 8; were observed. Proliferating cell nuclear antigen (PCNA) is a marker of cellular proliferation. Nucleoli are also increased in number and move to the nuclear margin in cases of cellular proliferation. The PCNA labeling index was calculated by counting the number of PCNA-positive cells per 2,000 tumor cells. PCNA labeling indices were 0.025% in the normal thyroid, 1.41% in follicular adenoma, 5.73% in atypical adenoma, and 6.16% in follicular carcinoma, respectively. Nucleoli retaining rate of the tumor cells were 40.0% in follicular adenoma, 63.7% in atypical adenoma, and 71.8% in follicular carcinoma. Rates of nucleolus margination were 20.9% in follicular adenoma, 34.4% in atypical adenoma, and 36.0% in follicular carcinoma. Changes in the basement membrane were morphologically classified into three groups as follows; membrane structure almost preserved (group I), partial discontinuity (breaks) (group II), and widespread absence of membrane structure (group III), based on immunohistochemical investigation of Type IV collagen. Group I was demonstrated in 8 cases of follicular adenoma and one case of atypical adenoma. Group II was observed in one case of follicular adenoma, 3 cases of atypical adenoma and 3 cases of follicular carcinoma. In addition, group III was noted in 3 cases of atypical adenoma and 5 cases of follicular carcinoma.(ABSTRACT TRUNCATED AT 250 WORDS)