Incidence and Histopathological Behavior of Papillary Microcarcinomas: Study of 429 Cases

Objective: We aim to present papillary microcarcinoma (PMC) incidence at a university teaching hospital, to compare characteristics of PMC in relation to size, and to assess for significant difference in PMC incidence among patients with non-PMC thyroid malignancies.

Materials And Methods: Pathology results were reviewed for consecutive total thyroidectomies between 2002 and 2007 (n = 860). Statistical significance was calculated using chi(2) or, when unavailable, Fisher exact test.

Results: PMC was found in 429 cases, which is 49.9 percent of all total thyroidectomies. In PMC > or =5 mm, 25.1 percent had extrathyroidal extension vs 9.1 percent for <5 mm (P < 0.001). When 4 mm is used as a threshold, P value was 300-fold smaller. Incidence in patients with any non-PMC thyroid malignancy was 51.6 percent against 47.2 percent in all other patients (P = 0.203).

Conclusions: In this study, PMC was found in 49.9 percent of patients, which, to our knowledge, is higher than any other reported incidence. A threshold of > or =4 mm was more significant than 5 mm for carrying increased risk for extrathyroidal spread. There was no significant difference in PMC incidence in patients with malignant vs benign disease.