Background: Papillary microcarcinoma (PMC) is increasing in incidence because of diagnosis by ultrasound-guided fine-needle aspiration cytology.
Methods: Between January 1966 and December 1995, we treated 6019 patients with papillary cancer; among them, 2070 patients with PMC were studied.
Results: PMC is essentially very similar to papillary cancer that is 11 mm or larger and has a very good prognosis. Smaller tumors and younger patients have a better prognosis. Among PMC, larger tumors (6-10 mm) recur in 14% at 35 years compared with 3.3% in patients with smaller tumors. Patients older than 55 years have recurrence in 40% at 30 years, with a worse prognosis than younger patients who have a recurrence rate of less than 10%. Extracapsular invasion by the primary tumor also has a higher recurrence rate. The majority of recurrences are in the neck. Therefore, annual ultrasound of the neck is effective for recurrence surveillance.
Conclusion: Papillary microcarcinoma is similar to larger papillary carcinomas with tumor characteristics and age-based recurrence rate that extends for many years, justifying long surveillance after surgery.