[Analysis of interlobar (between upper and middle lobes) lymph node enlargement on hilar tomography]

We examined interlobar (between upper and middle lobes) lymph node enlargement by compensating filter hilar tomography in cases of central vein type right upper lobe vein. The control group consisted of 100 randomly selected specimens, in which hilar lymphadenopathy such as malignant lymphoma or sarcoidosis, and displacement of interlobar fissure due to atelectasis or tuberculosis were excluded. Eighty-four of the control cases were central vein type. As a lung cancer group, 18 cases were analyzed. These cases consisted of central vein type, and interlobar lymph node enlargement was noted on operation, in the course of therapy or on enhanced CT study. The right hilum bordered by the upper lobe bronchus (medial to the orifice of B1) and segmental bronchus (B2 or B3) above, central vein lateral and intermedial arterial trunk on the mediastinal side were evaluated. The shadows that obscured the inner margin of the central vein and lower margin of the upper-lobe and segmental bronchi were analyzed. The inner margin of the central vein was visible in 75 cases (89.3%) in the control group, compared to 1 (5.6%) of 18 cases in the lung cancer group. Decreased radiolucency beneath the upper lobe bronchus and segmental bronchus was found in 10 cases (11.9%) in the control, compared to 16 cases (88.9%) in the lung cancer group. In conclusion, obliteration of the inner margin of the central vein and the opacity that decreased the radiolucency extending to the peripheral side of the upper lobe bronchus are strongly suggestive of interlobar lymph node enlargement. Recognition of interlobar lymph node enlargement is useful for the staging of lung cancer and diagnosis of the disease that accompanies systemic hilar lymphadenopathy.