Fine-needle aspiration of pulmonary hamartoma: A common source of false-positive diagnoses in the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytology

Context. - We use data from the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytology to evaluate the accuracy of fine-needle aspiration (FNA) biopsy for diagnosing pulmonary hamartoma (PH). Objective. - To use the performance characteristics of the PH cases in the Nongynecologic Cytology Program to determine the accuracy of FNA for identifying these lesions and to determine potential sources of interpretative errors. Design. - A retrospective review of the College of American Pathologists Nongynecologic Cytology cumulative data from 1997 to 2003 was performed to identify the overall accuracy of FNA for diagnosing PH and to determine the most common interpretative pitfalls. The slides from each of the cases of PH in the Nongynecologic Cytology Program were then reviewed in an effort to identify the cytologic characteristics that contributed to the poor performance of these cases. Results. - A. total of 766 participant responses for 19 PH FNA specimens were reviewed. The specificity of FNA for making the correct general reference interpretation of benign was 78%. The false-positive rate was 22%, with the most common false-positive diagnoses being carcinoid tumor, adenocarcinoma, and small cell carcinoma. The overall accuracy for making the correct specific reference diagnosis of PH was 26%. Microscopic review of the individual cases revealed possible explanations for some of the interpretative errors and the most frequent false-positive interpretations. Conclusions. - Cytologists should be aware of the potential false-positive interpretations that can occur in FNAs of PH and the potential reasons for these inaccuracies in order to minimize clinically significant diagnostic errors.