Follicular neoplasms of the thyroid: predictors of malignancy?

Follicular neoplasms of the thyroid present a therapeutic challenge. Initial limited thyroidectomy may result in some patients requiring completion thyroidectomy for malignancy. In the current study we examined age, gender, race, time from nodule discovery to operation in months, history of radiation exposure, tumor size (cm), and cell type in patients with follicular neoplasms identified at the time of thyroidectomy in two socioeconomically diverse settings from 1993 through 2000 to identify possible factors associated with a greater chance of malignancy. Of 36 follicular lesions identified in 35 patients seven (19%) were malignant on permanent section. Hurthle cell histology was present in six of 36 lesions. Mean age of patients with benign lesions was 47 +/- 13 versus 50 +/- 15 in malignant cases (P > 0.05). Benign lesions measured 2.6 +/- 1.2 cm versus 3.1 +/- 1.7 cm in malignant (P > 0.05). Other factors found not to be significant included gender and time nodule was present (12.8 +/- 19 months benign vs 11.8 +/- 20 months malignant) (P > 0.05). Hurthle cell histology was associated with a 50 per cent malignancy rate (three of six) versus 13 per cent (four of 30) with non-Hurthle cell histology (P < 0.05). Two patients with exposure to radiation fallout had malignancies in lesions of one and 2 cm (P < 0.05). Patients from a socioeconomically disadvantaged setting had a malignancy rate of 50 per cent (six of 12) compared with a malignancy rate of 3 per cent (one of 24) from a socioeconomically affluent population (P < 0.05). In conclusion Hurthle cell histology and exposure to radiation fallout were associated with significantly higher rates of malignancy in follicular neoplasms and should be taken into account when deciding on the initial extent of thyroidectomy. The difference in malignancy rates observed between socioeconomic settings while significant requires further investigation.