Three Distinctly Different Kinds of Papillary Thyroid Microcarcinoma should be Recognized: Our Treatment Strategies and Outcomes

Iwao Sugitani, Kazuhisa Toda, Keiko Yamada, Noriko Yamamoto, Motoko Ikenaga, Yoshihide Fujimoto

Papillary microcarcinoma (PMC) of the thyroid generally follows a benign clinical course. However, treatment strategies remain controversial. According to our previous retrospective review of 178 patients with PMC who underwent surgery between 1976 and 1993, the most significant risk factors affecting cancer-specific survival were clinical symptoms at presentation due to invasion or metastasis. Distant metastasis and cancer-specific death were never seen postoperatively for 148 cases (83%) of asymptomatic PMC without clinically apparent (>or=1 cm) lymph node metastasis or recurrent nerve palsy. Based on these results, we identified three biologically different types of PMC that should be treated differently. Type I comprises incidentally detected PMC without any symptoms, which is harmless and the lowest-risk cancer. Conservative follow-up with ultrasonography every 6 or 12 months is feasible. Type II involves the early stage of the usual low-risk papillary carcinoma. This can be treated by lobectomy when increasing size is noted during conservative follow-up. Type III comprises clinically symptomatic PMC, representing a high-risk cancer. Immediate wider resection followed by radioiodine treatment and suppression of thyroid-stimulating hormone is recommended.