Sonography: an underutilized diagnostic tool in the assessment of metastatic groin nodes

To assess the diagnostic value of gray-scale sonography in differentiating benign reactive nodes from metastatic nodes in the groin.

Twenty-seven patients with carcinoma of the penis, 3 patients with cutaneous melanoma, and 2 patients with squamous cell carcinoma of the lower extremity with inguinal lymphadenopathy were studied. A total of 122 nodes in the groin were examined sonographically using a 7.5-MHz probe. Sonographic features studied included lymph node size, longitudinal/transverse diameter (L/T) ratio, presence or absence of echogenic hilum, and appearance of the cortex. Pathologic confirmation was obtained via lymph node biopsy in 14 patients and groin dissection in 18 patients. Sonographic features were correlated with final pathology.

Forty-four of 122 nodes were metastatic and 78 were benign. L/T <2 had a sensitivity of 81% in the diagnosis of metastasis. Absent hilum had a sensitivity of only 68% but a specificity of 95%. An eccentric cortex was also highly specific for malignancy (96%). Presence of any sonographic feature suggestive of metastasis has a high sensitivity (95%) and negative predictive value (96%). The combination of L/T ratio <2 and absent hilum had the highest specificity (97%) combined with a high positive predictive value (93%).

Sonography is useful in the evaluation of groin nodes for metastatic disease. It can help select a suspicious lymph node for cytologic/histologic confirmation.