Biologic basis for the treatment of microscopic, occult well-differentiated thyroid cancer

Management of thyroid microcancer or occult well-differentiated thyroid cancer (OWDTC) is controversial. Our present study compared some clinical features of OWDTC and gross well-differentiated 10-mm thyroid carcinoma (GWDTC), which may offer a basis for treatment policy.

From 1964 to 2000, 1000 patients underwent thyroidectomy for thyroid cancer. We randomly selected 428 cases for study in which node sampling was carried out in 88% of GWDTC and 60% of OWDTC and who were demographically comparable. All data were obtained by chart review and analyzed by chi-square test.

With the maximum limit of 10 mm for defining OWDTC, we found 113 such cases with a mean size of 6.1 mm and 315 GWDTC cases with a mean size of 27.6 mm. The incidence of metastatic nodal disease was 16.8% in OWDTC cases and 25.7% in GWDTC cases (P = .057). Distant metastases occurred in 1 of 113 (0.9%) cases of OWDTC and 11 of 315 (3.5%) cases of GWDTC (P = .149). After a mean follow-up time of 55.8 months, neck metastatic recurrent disease occurred in 3 of 113 (2.7%) cases of OWDTC and 7 of 315 (2.2%) cases of GWDTC (P = .770). OWDTC was found in 11.1% of the GWDTC group undergoing an operation. Multicentricity occurred in 31.9% of OWDTC cases and 35.9% of GWDTC cases (P = .447). No cause-specific death occurred.

One cannot be dogmatic in treatment of microcancer, but one is justified in extending similar treatment principles for OWDTC as in GWDTC, which in our center usually indicates near-total thyroidectomy and consideration for radioactive iodine ablation.