Forty Years Following Pediatric Chondromixoid Fibroma of the Distal Femur: A Case Report and Review of the Literature

Background: Chondromyxoid fibroma (CMF) is a rare benign bone tumor, comprising less than 2% of all benign bone neoplasms. It predominantly affects young individuals and typically arises in the metaphysis of long bones. Despite its benign nature, CMF poses diagnostic and therapeutic challenges due to its potential for local recurrence and radiological resemblance to chondrosarcoma. Case Presentation: We report the case of a 9-year-old girl diagnosed with CMF of the distal femur in 1985. She underwent curettage twice, three years apart, with histological confirmation of CMF. Following surgical management, the patient remained asymptomatic and functionally unrestricted for nearly four decades. At the age of 49, she presented with medial knee pain unrelated to tumor recurrence. Imaging studies (MRI and CT) revealed multiple small, well-defined lesions in the left femoral diaphysis, radiologically consistent with residual CMF. The lesions were asymptomatic and biologically inactive. A multidisciplinary evaluation supported conservative management and follow-up imaging. Discussion: This case highlights the importance of long-term monitoring in patients with CMF and raises the question of whether late-appearing lesions represent true recurrence or post-surgical residuals. PET/CT may offer additional insight into the metabolic activity of such lesions, aiding in differentiation and treatment planning. Our case underscores the relevance of a tailored, patient-centered approach, leveraging modern imaging and minimally invasive diagnostics. Conclusion: CMF requires careful long-term follow-up due to the potential for recurrence and rare malignant transformation. This case demonstrates that residual lesions may persist without clinical consequences for decades and that advanced imaging techniques play a crucial role in ongoing evaluation and management.