Background: Fibrous dysplasia (FD) is a benign disorder of bone consisting of intramedullary proliferation of fibrous tissue and irregularly distributed, poorly developed bone. Although tumorlike in appearance, FD is probably a condition resulting from failure of maturation from woven to lamellar bone. The histology of FD has been well characterized since Lichtenstein first reported it, in 1938; however, the cytologic appearance has been described only rarely. To our knowledge, this is the first case report of fine needle aspiration (FNA) cytomorphology of FD.
Case: A 30-year-old female with breast carcinoma, diagnosed a month earlier, underwent computed tomography-guided FNA of a rib lesion radiologically thought to represent FD, although metastatic cancer could not be excluded. The smears contained blood, occasional osteoclastic multinucleated giant cells and frequent C-shaped fibrillary structures with dark central areas and lighter peripheries, representing woven bone. The cytologic/radiologic impression of FD was confirmed histologically.
Conclusion: FNA cytodiagnosis of FD is possible in the setting of consistent clinical and radiologic findings.