Atypical, polyarticular lipoma arborescens in a child

Area of Science:

• Orthopedics
• Radiology
• Pathology

Background:

• Lipoma arborescens is a rare, benign, tumor-like lesion characterized by villous proliferation of the synovium with mature fat.
• It typically affects the knee's suprapatellar recess but can involve other synovial structures.

Observation:

• A 12-year-old boy presented with symmetric involvement of bilateral bicipitoradial bursae, extensor tendon sheaths of both hands, and medial ankles.
• Magnetic resonance (MR) imaging suggested polyarticular lipoma arborescens.
• Histological examination confirmed the diagnosis following biopsies and surgical excision.

Findings:

• This case represents an exceedingly rare instance of polyarticular lipoma arborescens with symmetrical extra-articular and appendicular joint involvement.
• Histological analysis revealed associated non-necrotizing granulomatous synovial inflammation.
• The characteristic fatty signal on MR imaging is crucial for diagnosis.

Implications:

• The findings expand the understanding of lipoma arborescens presentation, particularly in pediatric cases with rare symmetrical involvement.
• MR imaging is a key diagnostic tool for identifying lipoma arborescens.
• This case underscores the importance of considering rare diagnoses in pediatric patients with polyarticular joint symptoms.