Lipoma with osteocartilaginous metaplasia in infrapatellar fat pad: A case report and review of literature.

Rationale: Lipomas are tumors composed of mature adipocytes, originating from the mesoderm, and are the most common soft tissue tumor. According to the World Health Organization classification of human soft tissue and bone tumors, there are 14 types of benign tumors, including mature adipose tissue. Osteolipoma is known as the rarest subtype of lipoma.

Patient Concerns: A 63-year-old female presented to our hospital for the evaluation and treatment of a palpable mass with pain in the right knee.

Diagnosis: The diagnosis was confirmed as lipoma with osteocartilaginous metaplasia.

Interventions: Surgical removal of the tumor was performed.

Outcomes: The main symptoms improved immediately after the surgery and recovered without any complications or recurrence until 2 years after surgery.

Lessons: Lipoma with osteochondral degeneration is a rare variant of lipoma and it is important to differentiate it from other malignant tumors. Pathological confirmation should be performed after marginal resection of the mass.