Diagnostic value of 18F-FDG PET/CT in the follow-up of conjunctival melanoma
摘要
To evaluate the diagnostic performance of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in detecting metastatic conjunctival melanoma (CM).
MethodsThis retrospective study enrolled 67 patients with histopathologically confirmed CM who underwent 18F-FDG PET/CT for follow-up or suspected recurrence. Parameters including short-axis diameter of lesions, maximum standardized uptake value (SUVmax), the target-to-nontarget (T/NT) ratios of cervical lymph nodes, and bone lesion characterization (osteolytic, osteoblastic, or unchanged) were evaluated. Metastases were confirmed via either histopathology or ≥ 6-month imaging follow-up. Diagnostic sensitivity, specificity, accuracy, and metastatic patterns were analyzed at patient level.
ResultsA total of 16 patients were confirmed metastasis. The median interval from surgery to metastasis was 20.3 months (range 1–100 months), with 56.3% (9/16) occurring within the first postoperative year. PET/CT detected metastases in 13 patients, missed metastases in 3 patients (2 with small preauricular lymph nodes and 1 with tiny pulmonary metastases), and misdiagnosed 1 patient with parotid benign nodules as metastatic. PET/CT demonstrated a sensitivity of 81.3%, specificity of 98.0%, and accuracy of 94.0%. The most common metastatic sites included lymph nodes (62.5%), bone (37.5%), lung (31.3%), and liver (25.0%), with PET/CT demonstrating detection rates of 95.5%, 100%, 86.7%, and 100%, respectively. PET/CT also identified metastases in rare sites, including the thyroid, cerebellum, adrenal glands, pericardium, pancreas, and subcutaneous/soft tissue. Lymph node metastases in CM predominately occurred in ipsilateral regional nodes (90.1%), with rare bilateral involvement (9.1%). Metastatic lymph nodes in the cervical and submandibular regions showed significantly higher mean SUVmax (11.6 ± 10.5 vs. 2.9 ± 0.9; p = 0.005) and T/NT ratios (6.9 ± 8.2 vs. 3.0 ± 1.0; p = 0.011) compared to inflammatory lymph nodes. SUVmax of metastatic lymph nodes, lung metastases, and liver metastases showed positive correlations with lesion size (p < 0.05 for all). Among metastatic lymph nodes, 53.2% had a short-axis diameter < 10 mm, and 59.1% of bone metastases exhibited no abnormal CT density.
Conclusion18F-FDG PET/CT provides high diagnostic accuracy in detecting systemic metastases of CM during follow-up assessments, particularly for small lymph nodes, early bone metastases, and uncommon sites.