Abstract
Background : Atypical thyroid adenoma, a rare tumor, is a variant of follicular adenoma with marked cytological atypia. We report two cases of atypical thyroid adenoma, difficult to accurately diagnose in fine-needle aspiration cytology (FNAC) and discuss their biological neoplastic cell features.
Case 1 : A 72-year-old woman was found to have a mass 4 cm in diameter in the left thyroid lobe. Pre-operative FNAC smears suggested a diagnosis of “malignant, suspected carcinoma”.
Case 2 : A 38-year-old woman was found to have a mass 7.5 cm in diameter in the right thyroid lobe. Pre-operative FNAC smears, suggested a diagnosis of “Class 3, suspected oxyphilic adenoma”.
In both cases, histological findings for the resected tumor were compatible with atypical thyroid adenoma. Immunohistochemically, tumor cells were highly positive for TP53INP1 and p53.
Conclusions : It is difficult to accurately diagnose atypical adenoma based on cytological thyroid findings alone. The detection of follicular cells with markedly nuclear atypia in cytological specimens, necessitates a judgment of cytological diagnosis, together with clinical information. Immunohistological findings for TP53INP1 and p53 suggested that atypical adenoma tumor cells may be malignant.
