[Thyroid oncocytic adenoma. A review of the morphological spectrum in four cases].

Oncocytic change involves a cytoplasmic enlargement due to mitochondrial accumulation observed in a wide variety of conditions and in multiple organs. It can be reactive or neoplastic. In the thyroid gland, this change is a metaplastic phenomenon that takes place under different circumstances that promote cellular stress, and could even produce a true neoplasm, both benign or malignant. The oncocytic adenoma, a malignant tumor will be described. We analyzed four cases studied at the surgical pathology department of the American British Cowdray Medical Center in Mexico City that displayed unusual cytomorphological features. They became a diagnostic challenge and in order to solve it we reviewed their morphological spectrum. Tumor characteristics in all cases included: massive ischemic necrosis short after a fine needle aspiration biopsy was performed, unexpected large size, coexistence with a malignant independent neoplasm and cytological features similar to those observed in papillary carcinomas. It is of utmost importance for the pathologist to acknowledge the existence of these features in order to avoid diagnostic mistakes that could lead to unsuccessful treatment.