Role of Doppler color in the differential diagnosis of benign and malignant adenopathies

The diagnosis of enlarged lymph nodes is of the utmost importance especially in the treatment planning of cancer patients. US yields such morphological findings as node size, longitudinal/transverse diameter ratio, hilum visibility and cortical thickness, which however do not permit the differential diagnosis of benign from malignant forms. Some authors tried to distinguish inflammatory enlargement from metastatic forms on the basis of color Doppler findings, with conflicting and questionable results. We investigated the potentials of color Doppler US in the differential diagnosis of benign and malignant lymph node enlargement using morphological data and flow measurements in lymphatic hilum vessels. The palpable superficial lymph nodes of 70 patients were studied with color Doppler with a linear probe (7.5-10 MHz) equipped for Doppler flow measurements. The largest lymph node was studied in multiple enlargement. The final diagnosis was made with US-guided cytology and/or excisional biopsy. The venous hilar vessels were depicted with color Doppler US in 44/45 patients with lymphadenitis and only in 1/17 patients with metastatic enlargement. Spectral Doppler exams of the hilar arteries showed flows with a wide telediastolic component in lymphadenitis (relative RI:0.58), while flow was rapid and with poor telediastolic component (relative RI:0.84) in metastatic enlargement. Average RI was 0.62 in Hodgkin's lymphomas and 0.71 in all the other lesions. We conclude that the distortion and compression of the main hilar vessels in metastatic lymph node enlargement often prevents color Doppler depiction of venous vessels. Moreover, the compression and distortion of the intranodal capillary network (the "mass" effect) often results in increased RI, as detected with power Doppler in the lymphatic hilum. Even though color Doppler US studies of the hemodynamic changes in the hilar vessels need further validation in larger series of cases, our preliminary results suggest interesting potentials in distinguishing inflammatory from metastatic enlargement, which differentiation remains nevertheless difficult especially in Hodgkin's lymphoma.