Aims: Standard practice is to take one section from every lymph node found in colorectal carcinoma resection specimens, to look for metastatic carcinoma. This study evaluates whether assessing three sections separated by 100 microm detects significantly more metastases in nodes than the conventional single section.
Methods: A retrospective study of 100 colorectal carcinoma resection specimens. All blocks containing lymph nodes had two extra histological sections cut (separated by 100 microm) and stained with haematoxylin and eosin. The original slide was called level 1, and the extra two sections levels 2 and 3.
Results: Twenty Dukes's A (equivalent to WHO-UICC stage grouping I, pTNM stage pT1/2N0), 43 Dukes's B (equivalent to WHO-UICC stage grouping II, pTNM stage pT3/4N0), and 37 Dukes's C (equivalent to WHO-UICC stage grouping III, pTNM stage at least pN1) cases were examined (total 1453 nodes). Twelve extra metastases (in 11 patients) were discovered in nodes at levels 2 and 3, which were negative in level 1. Ten cases were Dukes's C and, in one patient, this led to upstaging from N1 to N2 (pTNM classification system). One case was Dukes's B and the discovery of a single metastasis on level 2 upstaged it to Dukes's C.
Conclusions: Triple levelling detected more tumour deposits than the conventional single section. In two patients, the staging classification of the lesion was changed, with potentially important implications for prognosis and management.