PAPILLARY AND FOLLICULAR THYROID CARCINOMAS WITH AN INSULAR COMPONENT

Background. Papillary (PC) and follicular (FC) thyroid carcinomas may have a focal or predominant insular component (IC). This study correlates histologic behavior with the extent of the IC of these tumors. Methods. Forty-one thyroid carcinomas (17 follicular variants [FV] of PC, 24 FC) with focal or predominant IC were reviewed. The tumors were stained with carcinoembryonic antigen, thyroglobulin, and calcitonin. DNA ploidy analysis was done on 18 tumors on paraffin-embedded tissue. The IC was correlated with age, stage of disease, follow-up, and ploidy analysis by Fisher's exact two-tailed test. Results. No tumor was purely insular. IC was minor (10-40% tumor area) in 16 and predominant (50-90%) in 25. Nuclear features in IC included typical FC nuclei in 14, FVPC nuclei in 16, and intermediate-type nuclei in 16 tumors. Vascular invasion was seen in 22, necrosis in 10, and sclerotic stroma in all. Fourteen tumors were confined to the thyroid, 13 showed regional spread, and 9 had distant metastases; five patients are dead of disease and six are alive with disease. Thirteen tumors were diploid, three tetraploid, and two hyperdiploid aneuploid. There was no correlation of quantity of IC with tumor stage, follow-up status, or ploidy. Conclusion. IC within PC and FC does not adversely affect prognosis.