Papillary thyroid microcarcinoma: extrathyroidal extension, lymph node metastases and risk factors for recurrence in a high prevalence of goiter area

BACKGROUND. Papillary thyroid microcarcinoma (PTMC) is diagnosed with increasing frequency. Since risk factors for an aggressive clinical behavior have not been clearly delineated, the best therapeutic option and follow up protocol for PTMC have not been established yet, especially in case of incidental diagnosis after partial thyroidectomy for benign disease. We reviewed our series of patients with PMTC to determine risk factors for recurrence in a high prevalence of goiter area. METHODS. The medical records of all the patients who underwent total thyroidectomy (TT) with a final pathology report of PTMC between October 2002 and June 2007 were reviewed. Demographic, clinical and pathological characteristics were registered. PTMC was defined as a papillary thyroid carcinoma 10 mm in diameter. Follow up evaluation was obtained by outpatients consultation and/or telephone interview. Patients who completed follow up evaluation were included in this study. RESULTS. Among a series of 2220 patients who underwent thyroidectomy for a thyroid carcinoma, 1029 had a PTMC. Among them, 965 underwent TT and were included. Follow up evaluation was completed in 200 patients. There were 40 males and 160 females, with a mean age of 49.4 years (range 11-81). Diagnosis was incidental in 175 patients (87.5%). PTMC were larger than 5mm in 145 patients (72.5%) and multifocal in 88 (44%). Extracapsular spread (ECS) was present in 41 cases (20.5%), node metastases in 20 (10%) and distant metastases in 2 (1%). Loco-regional recurrence was observed in 43 cases (21.5%). Patients with ECS were significantly younger (43.4 Vs 51.0 years) (P<0.005) and had more frequently a multifocal disease (24/41 Vs 63/159) (P<0.05). Patients with node metastases were significantly younger (36.7 Vs 51.0 years) (P<0.005), more frequently males (8/20 Vs 32/180) (P<0.05) and had more frequently a pT3 tumor (12/20 Vs 29/180) (P<0.001). Risk factors for recurrence were male sex, multifocal disease, ECS and node metastases at diagnosis (P<0.05). Lesion size <5mm was not associated with a lower rate of ECS, node metastases and recurrence. CONCLUSIONS. Incidental diagnosis of PTMC is frequent in a high prevalence of goiter area. PMTC showed variable aggressiveness, independent from tumor size. The extent of surgery, the need for radio-iodine ablation and follow up protocol should be based on prognostic parameters, such as gender, multifocality, ECS and node metastases at diagnosis, as for larger tumors.