Fine needle aspiration cytology of late-stage callus in stress fracture - A case report

BACKGROUND: Fine needle aspiration cytology (FNAC) is effective in the diag nosis of bone lesions when combined with careful radiologic and clinical ev aluation. The cytologic features of callus have not been described before i n the English-language literature. CASE: An 18-year-old female presented with a pain in the right lower leg th at had been present for two months. Clinical and radiologic findings sugges ted either stress fracture or periosteal osteosarcoma. The aspiration speci men showed individually scattered, oval cells with moderate amounts of pale pink cytoplasm. The cells contained a single eccentrically located nucleus with evenly distributed, fine chromatin. Osteoclastic giant cells were sca ttered in the smears. A cytologic diagnosis of benign bone-formation lesion , compatible with callus in fracture, was made. The diagnosis of late-stage callus was confirmed by subsequent histologic examination. CONCLUSION: Typical cases of stress fracture do not need histologic Examina tion, but some cases may be confused with benign and malignant bone tumors. The typical and unique cytologic features of late-stage callus combined wi th clinical and radiologic findings may prevent the use of more invasive di agnostic procedures and can be a choice for management.