Fine-needle aspiration cytology of bone: accuracy and pitfalls of cytodiagnosis.

Background: Fine-needle aspiration cytology has proved to be an accurate, cost-effective, and safe technique for diagnosing inflammatory and neoplastic lesions at different body sites. Its applicability in bone pathology, however, has been controversial due to a high percentage of inadequate samples and nonspecific results in the diagnosis of primary bone lesions. In this study, the diagnostic accuracy of the technique and its capacity for diagnosing primary bone lesions were assessed. In addition, the authors analyzed the diagnostic limitations with focus on specimen adequacy.
Methods: The authors reviewed 314 consecutive fine-needle aspirations of bone from 308 patients. Direct or cytospin smears from aspirated material were fixed in 95% alcohol and stained by a modified Papanicolaou technique. Ninety-seven smears (31%) initially were considered unsatisfactory and excluded from the study. A diagnosis was rendered in 217 cases (69%), which were classified into 4 categories: primary bone lesions (benign and malignant) (42%), metastatic bone tumors (37%), suspicious for malignancy (5%), and negative (16%).
Results: The overall accuracy was 95%. Seventy-eight percent of primary bone lesions were correctly diagnosed by cytology. All cases diagnosed as metastatic by cytology were correct. The authors encountered difficulties diagnosing fibro-osseous lesions. Thirteen percent of cases were erroneously diagnosed as "negative" or "inflammatory conditions." On review, the absence of adequate cytologic material was noted in all of them. This sampling error could have been avoided by the presence of an on-site cytopathologist.
Conclusions: Fine-needle aspiration of bone is a simple, reliable, and accurate diagnostic technique that can facilitate patient management and preoperative decision-making and/or avoid unnecessary invasive procedures for patients with primary or metastatic bone lesions. However, the radiologist, cytopathologist, and orthopedic surgeon should work together for optimal results. Moreover, a definitive pathologic diagnosis should not be issued if diagnostic material is not adequate and/or clinicoradiologic information is incompatible.