Der diagnostische Stellenwert der MIB-1- und PCNA-Immunhistometrie in der Differentialdiagnostik follikulärer Schilddrüsentumoren

摘要

The diagnostic value of MIB-1 and PCNA immunohistometry in differential diagnosis of follicular tumors of the thyroid gland The cellular prolifarative activity MIB-1 and PCNA immunopositivity of normal tissue (n = 30), follicular adenoma (n = 21) and follicular carcinoma (n = 28) of the thyroid gland was analysed by means of immunohistometry. Immunohistochemical reactions were performed on 3-µm sections from routinely formalin fixed and paraffin embedded surgical specimens using the indirect peroxidase method. The rate of immunostained cells was determined using the CM - 2 TV image analysis system (Hund, Wetzlar, Federal Repuplic of Germany). Mean MIB-1and mean PCNA immunopositivity was higher in follicular carcinoma (MIB-1mean 2,52%, PCNAmean 1,49%) and in follicular adenoma (MIB-1mean 0,69%, PCNAmean 0,42%) than in normal thyroid tissue (MIB-1mean 0,14%, PCNAmean 0,05%).The distribution of single values differed significantly between groups. To test the suitability of MIB-1 and PCNA immunohistometry for differential diagnosis of follicular adenoma and follicular carcinoma, different four-field tables with varying thresholds were calculated. Using a threshold for MIB-1mean of 0,8%, follicular carcinoma could be detected with a sensitivity of 82,1% (23/28) and a specivity of 76,2% (16/21). Using a threshold for MIB-1mean of 1,3% a specivity of 90,5% is reached while the sensitivity decreases to 64,3%. With a PCNAmean threshold of 0,5% a follicular carcinoma could be detected with a sensitivity of 64,3% (18/28) and a specivity of 71,4% (15/21). Using a threshold for PCNAmean of 0,9% a specivity of over 90% is reached (90,5%; 18/21) while the sensitivity decreases to only 50% (14/28). A great overlap of low single values for MIB-1mean and PCNAmean was found in follicular adenoma and follicular carcinoma of the thyroid gland. Only one follicular adenoma showed a higher MIB-1mean immunopositivity than 2% and only one follicular adenoma had a PCNAmean immunopositivity of more than 1%. MIB-1 and PCNA immunohistometry cannot be recommended for differential diagnosis of follicular lesions in routine surgical pathology. In difficult differential diagnosis between follicular adenoma and carcinoma a MIB-1mean value > 2% and a PCNamean value > 1% could be a hint for malignancy and more tumor material should be embedded and / or serial sections should be performed in order not to miss rupture of the tumor capsule and / or infiltration of the blood vessels.