Differential Diagnosis of Oncocytic Lesions of the Breast and Thyroid Utilizing a Semiquantitative Approach

OBJECTIVE: To assess whether a light microscopic, semiquantitative approach could reliably distinguish between benign nonneoplastic, benign neoplastic and malignant oncocytic lesions of the breast and thyroid. STUDY DESIGN: Alcohol-fixed, Papanicolaou-stained fine needle aspiration smears of histologically proven goiter and chronic thyroiditis (18 cases), Hurthle cell adenomas (7 cases), Hurthle cell carcinomas (6 cases), fibrocystic disease (17 cases), papillomas and papillomatosis (7 cases) and apocrine carcinomas (6 cases) were rated by three independent observers using the following 10 cytologic criteria: cellularity, nuclear-cytoplasmic ratio, multinucleation, nuclear size, nuclear shape, anisonucleosis, multinucleolation, nucleolar-nuclear ratio, nucleolar size and nucleolar shape. Each of these 10 cytologic criteria was rated using a 1-3 scale. The scores for all 10 features were summed to give a total score for each case. The total scores were statistically analyzed to determine the validity and reproducibility of the summed criteria. RESULTS: The summed criteria of the total scores were reproducible between the three observers, with standard deviations ranging from 1.36 to 2.88 for thyroid and 1.72 to 2.00 for breast oncocytic lesions. The ability of the total scores to differentiate benign from malignant oncocytic lesions of the breast and thyroid was confirmed by a positive predictive value for malignancy of 67% for thyroid and 72% for breast and a negative predictive value for malignancy of 100% for nonneoplastic oncocytic lesions and >90% for benign oncocytic neoplasms in both. The Kruskal-Wallis test revealed that the total scores were able to distinguish three diagnostic categories of nonneoplastic, benign neoplastic and malignant oncocytic breast and thyroid lesions, with P