Prognostic value and significance of subcarinal and superior mediastinal lymph node metastasis in lower lobe tumours

Abstract

The new seventh edition of the tumour, node and metastasis (TNM) classification now groups part of the #10 lymph nodes, which include the subcarinal space along with the inferior border of the main-stem bronchus (#10 below), as being a part of the 'subcarinal zone'. In this retrospective study, we aimed to evaluate the clinical significance of including the '#10 below' lymph node with the 'subcarinal zone'. Between 1980 and 2002, the locations of the 66 pN1 and 83 pN2 were found to be part of the bilateral lower lobe in 149 patients. The group comprised 107 males and 42 females, with ages ranging from 16 to 81 years (median: 61.4 years). The clinicopathological records were examined with regard to age, sex, nodal status, T factor and histological type. These variables were analysed as risk factors for superior mediastinal lymph node (SML) metastasis and prognosis. Of 149 cases, 28 were #10 below positive/#7 negative (only #10 group), 29 were #10 below negative/#7 positive (only #7 group) and 37 were #10 below positive/#7 positive (double-positive group). There was a significantly higher incidence (64.9%, 24/37) of SML metastasis for the double-positive group as compared to only #10 (14.3%, 4/28) and only #7 groups (31.0%, 9/29) (P<0.001). The overall 5-year survival rates for the only #10, only #7 and the double-positive groups were 50%, 28% and 22%, respectively (P=0.02). As compared to #10 metastasis, #7 metastasis is a prognostic risk factor for highly advanced SML metastasis and a poorer prognosis. Therefore, since #10 below and #7 provide different types of diagnostic information, they may not be bundled together during patient evaluations.