Size and histologic characteristics of lymph node material retrieved from tissue discarded after routine pathologic examination of lung cancer resection specimens

Redissection of discarded lung resection specimens after routine pathology examination reveals missed lymph node metastasis. We sought to determine if size can be used to grossly select lymph nodes for microscopic examination. This is a prospective cohort study of lymph nodes retrieved from discarded lung resection specimens. The association between size and histologic characteristics of retrieved material was compared by the Wilcoxon-Mann-Whitney test. We retrieved 1094 grossly 'lymph node-like” tissue from 112 remnant lung resection specimens, of which 345 (32%) proved not to be lymph nodes and 71 (9%) of 749 lymph nodes had metastasis. Metastasis was present in discarded nodes in 26 (23%) of 112 patients. The non-lymph node tissue was significantly smaller than lymph nodes (P < .0001); lymph nodes with metastases were significantly larger than those without metastases (P < .0001). However, there was significant size overlap between the 3 types of grossly lymph node-like tissue. Thirty-two percent of nodes with metastasis were less than 1 cm; 15% of patients had at least 1 lymph node less than 1 cm with metastasis. The size difference between lymph nodes with and without metastasis is clinically unhelpful because of broad overlap. Size is insufficiently discriminatory and cannot be relied on to select materials for histologic examination. A third of grossly retrieved material was non-lymph node tissue. This probably occurs during routine pathologic examination and likely contributes to the low N1 lymph node count.