Keratin-Positive Giant Cell-Rich Tumor in Early Infancy: Metastatic Presentation and Imatinib Response

Background: Keratin-positive giant cell-rich tumor (KPGCT) is a rare bone and soft tissue neoplasm, with pediatric and metastatic cases being exceedingly uncommon. Observation: We report a 1.5-month-old male infant presenting with multifocal metastatic disease involving the skull, adrenal glands, vertebrae, mandible, soft tissue, and long bones. Histopathologic evaluation confirmed KPGCT, molecular testing was negative for HMGA2 rearrangement. Treatment with imatinib resulted in marked regression of lesions and clinical improvement without toxicity. Conclusions: This case expands the clinical spectrum of pediatric KPGCT and suggests that imatinib may be an effective treatment option in infants with advanced disease, even canonical HMGA2::NCOR2 fusion absent.