Differential Diagnosis for the 35-year-old Male Patient
The patient presents with a palpable mass in the medial region of the right knee, which is firm, non-tender, and immobile. The following differential diagnoses are considered:
- Single most likely diagnosis
- Ganglion cyst: A common benign lesion that can occur near joints, tendons, or ligaments, often presenting as a firm, non-tender mass. The location along the medial joint line, adjacent to the medial collateral ligament, and the ultrasound findings of cyst-like areas or focal fluid collections support this diagnosis.
- Other Likely diagnoses
- Bursitis or bursal cyst: Inflammation of a bursa or a fluid-filled sac that can occur near joints, which may present as a palpable mass. The ultrasound findings of a possible recess from the joint or bursa suggest this possibility.
- Meniscal cyst: A cyst that can occur in association with a meniscal tear, although the negative McMurray's test and lack of symptoms suggestive of meniscal pathology make this less likely.
- Lipoma or soft tissue tumor: A benign tumor of fat cells or other soft tissue, which can present as a firm, non-tender mass.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Soft tissue sarcoma: A rare but potentially life-threatening malignancy that can present as a mass in the soft tissues. Although unlikely, it is essential to consider this diagnosis to ensure prompt evaluation and treatment if necessary.
- Infection or abscess: A collection of pus that can occur in the soft tissues, which may present as a palpable mass. Although the patient denies pain, erythema, or increased warmth, infection remains a possibility.
- Rare diagnoses
- Synovial chondromatosis: A rare condition characterized by the growth of cartilage in the synovial membrane, which can present as a mass or multiple masses in the joint.
- Pigmented villonodular synovitis (PVNS): A rare condition characterized by inflammation and overgrowth of the synovial membrane, which can present as a mass or joint swelling.