Fine-needle biopsy of pediatric lesions: a three-year study in an outpatient biopsy clinic.

Diagnostic Cytology Laboratory, Inc., has an outpatient Fine Needle Biopsy Clinic, which evaluated 7,487 fine-needle biopsies (FNB) from January 1989 to February 1992. Two hundred eighty-eight (3.8%) of these specimens were collected from patients 19 years old or younger and this represents the largest study of this population in the scientific literature. The majority of these specimens were obtained from palpable masses in the head and neck region [lymph nodes (58.3%), thyroid (7.6%), and salivary gland (5.2%)] while a smaller number were collected from miscellaneous soft tissue (18.8%) and breast masses (10.1%). Thirteen (4.5%) (from 12 patients) were diagnosed as malignant by FNB and 275 (95.5%) (264 patients) were benign by FNB. This benign:malignant ratio (22:1) is significantly higher than has been reported from tertiary care institutions and is a reflection of the difference of this outpatient population. Two hundred nine of 276 patients (75.7%) had adequate follow-up, including 137 (49.6%) patients followed by observation, 48 (17.4%) patients followed by surgical biopsy, and 24 (8.7%) patients followed by some other modality: imaging studies, flow cytometry, or treatment. There was a single false positive diagnosis (a pilomatrixoma) and one (1) false negative interpretation (a cystic acinic cell carcinoma) resulting in a diagnostic sensitivity of 92.3% and a specificity of 99.6%. The positive predictive value was 92.3%, the negative predictive value was 99.6%, and the test efficiency was 99.3%. The utility, cost-effectiveness and uniqueness of the clinic population is discussed.