Non-diagnostic cytological outcome of thyroid biopsy and the risk of thyroid malignancy.

This study assessed the incidence of neoplasms, including malignant tumors, in lesions within the thyroid gland from which non-diagnostic biopsy aspirates were obtained. An auxiliary goal of the study was an evaluation of the diagnostic efficacy of repeated biopsy in cases when the first biopsy was non-diagnostic. Thus, results of 4603 fine-needle aspiration biopsies (FNABs) were submitted to histopathological verification. The verification revealed the rate of malignancy at 7.1% for non-diagnostic biopsies, i.e., significantly higher (p < 0.001) than that in cases FNAB-diagnosed as benign lesions (2.1%). Repeated biopsy, performed when inadequate material has been collected, seems to be less effective than the first biopsy (non-diagnostic specimens: 14.4% vs 8.9%; p < 0.01). The occurrence of neoplasms in the goiter was significantly higher (p < 0.0001) in patients with non-diagnostic first FNAB than in those with diagnostic one (50.7% vs 33.5%, p < 0.001). And again, in patients with two non-diagnostic FNABs, the occurrence of neoplasms was higher than that in patients with the second diagnostic cytology (63% vs 41.2%, p < 0.05). According to our data, patients with non-diagnostic FNAB results should be very carefully monitored, especially when the repeated biopsy is either non-diagnostic again or not performed at all.