A 20-Year-Old Woman with Metachronous Polyostotic Simple (Unicameral) Bone Cysts in 9 Sites: A Case Report.

BACKGROUND Simple (unicameral) bone cysts (SBCs) are benign, fluid-filled bone lesions that are typically solitary and can be unicameral (single chamber) or septated. Most commonly affecting the long bones of children and adolescents, SBCs can be asymptomatic or associated with pain or fractures. Multifocal SBCs, featuring multiple cysts across different bones, are exceptionally rare and pose unique diagnostic and therapeutic challenges.