Representativeness of radiologically guided fine-needle aspiration biopsy of bone lesions

The consistency of the cellular yield as obtained by radiologically guided fine-needle aspiration biopsy (FNAB) was investigated in 29 cases with bone lesions. Aspirates from three different sites of the same lesion were analysed randomly and independently by two cytologists unaware of the clinical and radiological findings.The series was grouped cytologically into four categories: (1) benign, (2) sarcoma, (3) other malignancy, (4) non-conclusive. A lesion was considered cytologically homogenous, when all three aspirates were identically categorised. Among 29 lesions, 13 and 12, respectively, were assessed as homogeneous by the two cytologists. In the remaining lesions, heterogeneity almost exclusively pertained to the mixture of conclusive and non-conclusive aspirates. An alternative diagnosis was suggested in one case by each cytologist. Comparison of the two cytologists' assessments showed that 21 cases were compliant, i.e., no inter-observer difference in 63 out of 87 aspirates. In the remaining eight cases (24 aspirates), non-compliance was mainly due to differences between the cytologists in the ratio of conclusive versus non-conclusive aspirates. Only the analysis of one and the same aspirate resulted in two different diagnoses. A correct diagnosis was given by the cytologists in 22 and 23 cases, incorrect in two and non-conclusive in five and four, respectively.Our cytological study of bone lesions, albeit limited, suggests that true tumour heterogeneity is rare. The non-compliance between the two cytologists and the diagnostic difficulties should mainly be attributed to the blind, random approach of the study.The main problem of FNAB pertains to the high rate of non-conclusive aspirates.This, however, does not entail an increased risk of incorrect diagnosis, but rather prompts repeat FNAB.