Pediatric patient with upper humerus lytic lesion with cortical thinning which is not a treatment modality
Simple/ Solitary/ Unicameral-Bone Cyst
a. It nearly always occur during first two decades of life, most often between 4— 10 years of age, & usually in males (M : F= 2.: 1).
b. It always arise in juxtaphyseal metaphysis. and sometimes extends upto diaphysis but never cross physis to involve ephysis and joint. The majority of cysts occurs in metaphyseal region of proximal humerus (50%) and femur (25%)Q. The next most common sites are proximal & distal tibia.
c. Mostly asymptomatic, as because of only mild expansion of bone, the pain and swelling are usually very mild.
d. That is why, the condition is usually discovered after pathological fracture from a trivial trauma, or as an incidental finding on x - ray.
a. On x ray it is centrally located, radiolucent lesion of the metaphysis that is slightly and symmetrically expansile. Fallen leaf (fragment) sign is pathognomic manifestation and represents that fractured fragment of bone settles to the most dependent portion of cyst because of unicompartmental nature.
b. The differential diagnosis of simple bone cyst include aneurysmal bone cyst, monostotic fibrous dysplasia, atypical esoinophilic granuloma non ossifying fibroma and other benign cartilage tumor egenchondroma
Histopathology of Unicameral Bone Cyst
a. Single cavity lined by thin layer of flimsy fibrous tissue often containing giant cells. The thin membranous lining is composed primarily of epithelial like cell.
b. Treatment includes observation with restriction of activities (for asymptomatic small lesions), aspiration of fluid and injection of methyl prednisolone (for active cysts abutting physeal plate).
c. Sclerosants are also used for UBC
d. Curettage and bone grafting is done for enlarging lesions (even after steroid injection), large cyst at high risk of fracture and if pathological fracture develops or cyst in the proximal femur.