Papillary microcarcinoma and papillary cancer of the thyroid ≤1 cm -: Modified definition of the WHO and the therapeutic dilemma

Aims: Major controversies exist regarding the treatment of papillary microcarcinoma of the thyroid (PMC). Prior to 2003 PMC was defined by the WHO as a papillary carcinoma of 1cm or less in diameter. In 2004 that definition changed, with the new classification requiring that the tumour also must be found incidentally. Patients, methods: In this study we reviewed the clinical records of 67 patients with papillary tumours of the thyroid <= 1cm, taking into account the new WHO definition (54 pts. with incidentally found PMC, median age: 53 years, 13 pts. with suspicion of thyroid neoplasm before resection, median age: 38 years). Clinical presentation, surgical treatment, further therapy and follow-up are presented. Results: Median tumour size was 7 mm in both groups (1-10 mm). Multicentric tumours were found in 15 pts. (22%), 8 had more than one PMC on the same side, and 7 displayed PMC bilaterally. Eleven (16%) of the primary tumors had metastatic involvement of regional lymph nodes at the time of initial surgery or during follow-up. Two patients showed distant metastases. No correlation between tumour size and multifocality or the presence of lymph node metastoses could be seen. The gender of patients was the only significant independent variable for all patients; age and lymph node involvement was significantly different between incidentally and non-incidentally found PMC. Conclusions: Despite the mojority of patients with PMC having an excellent outcome, there are also cases showing an unfavorable course. Currently no predictive parameter exists to anticipate the course and long-term outcome for an individual patient. Until this problem is solved, each patient should have the option to decide for him or herself whether to be treated similarly or differently than for conventional thyroid cancer.