When is a meniscal cyst not a meniscal cyst?

Area of Science:

• Orthopedic Surgery
• Radiology
• Oncology

Background:

• Meniscal cysts adjacent to the knee joint line are often diagnosed using clinical examination and magnetic resonance imaging (MRI).
• These cysts are typically associated with meniscal tears, but their imaging characteristics can vary.

Observation:

• Two patients presented with knee joint line lesions initially diagnosed as meniscal cysts via clinical and MRI assessment.
• Neither patient had apparent meniscal tears, and MRI revealed non-homogenous signal intensities within the lesions.
• These imaging findings led to surgical management plans unsuitable for the eventual diagnoses of fibromyxoid sarcoma and monophasic synovial sarcoma.

Findings:

• Non-homogenous MRI signals in suspected meniscal cysts can be attributed to factors like hemorrhage or high protein content fluid.
• The absence of a meniscal tear, coupled with mixed MRI signals, necessitates careful consideration before diagnosing a meniscal cyst.
• The study highlights that not all meniscal cysts are linked to meniscal tears.

Implications:

• Diagnostic imaging alone may be insufficient for definitive diagnosis of knee joint line lesions, especially with atypical MRI findings.
• A cautious approach is recommended for diagnosing meniscal cysts when MRI shows mixed signals and no meniscal tear is evident.
• Shared management involving orthopedic surgeons, radiologists, and oncologists is crucial for obtaining a tissue diagnosis prior to definitive treatment, preventing inappropriate surgical interventions for potential sarcomas.