Focal periphyseal edema with atypical MRI features: Biopsy findings and imaging follow-up.

Focal periphyseal edema (FOPE) is a magnetic resonance imaging (MRI) finding centered on the closing physis of the adolescent knee and generally regarded as a benign, self-limiting manifestation of physiologic physeal fusion. To date, no report has described biopsy findings in FOPE, as the diagnosis has relied exclusively on imaging characteristics and clinical follow-up. An 11-year-old male competitive swimmer presented with a 2-month history of atraumatic right anterior knee pain. Radiographs were unremarkable. Laboratory studies showed no evidence of inflammation. MRI demonstrated T2-hyperintense signal on both sides of the distal femoral epiphyseal plate, with extension to the adjacent medial metaphyseal cortex and gadolinium enhancement suggestive of physeal destruction. Given the imaging appearance and a differential diagnosis of osteosarcoma, chondroblastoma, giant cell tumor, and osteomyelitis, an image-guided core needle biopsy was performed to exclude aggressive pathology. Histopathology demonstrated normal tissue without inflammatory or neoplastic cells, and cultures were sterile. These findings excluded malignancy and infection in the sampled tissue, and a presumptive diagnosis of FOPE was made, and the patient was managed expectantly. At 3-month follow-up, the patient was asymptomatic, and repeat MRI showed marked interval improvement of the previously noted findings, although faint residual signal persisted. In this case, biopsy served to exclude aggressive disease rather than to confirm a specific histologic pattern of FOPE, and the diagnosis was ultimately supported by the subsequent clinical resolution and imaging improvement. These findings support a conservative, noninvasive diagnostic and management approach when imaging findings are otherwise typical of this entity.