Fine-needle aspiration of fibrous dysplasia of bone: a worthwhile endeavor or not?

Fine-needle aspiration (FNA) is a minimally invasive technique which is enjoying ever-increasing popularity in the initial diagnosis of many pathologic processes. However, FNA diagnosis of neoplasms occurring within bones is less commonly employed and is not the preferred method in some types of bony lesions. Fibrous dysplasia is a primary neoplasm of bone for which it is not yet clear whether FNA can reliably yield adequate diagnostic material. Review of data from 82 cases of fibrous dysplasia diagnosed between 1990 and 2006 yielded six cases, in which diagnosis was initially attempted by FNA prior to open biopsy and surgical resection. Corresponding cytologic, histologic, and imaging characteristics of the cases were reviewed. Of the six cases in which initial diagnosis was attempted by FNA, only two of six (33%) yielded adequate diagnostic material. Smears of aspirated material in all cases contained nonspecific elements, including fragments of benign host bone and cartilage, bland stromal cells, adipocytes, blood, and debris. Importantly, the two positive FNA cases were dependent on the concurrent core needle biopsy (all smears of aspirate material were nondiagnostic). Even with image guidance, FNA is insufficient to obtain diagnostic material for cases of suspected fibrous dysplasia of bone. Core needle biopsy at least is recommended to obtain adequate material, and to reduce the risk of misdiagnosis due to sampling error.