DNA content in primary tumours and lymph node metastases in colorectal adenocarcinoma

In 18 consecutive patients operated on for colorectal carcinoma of Dukes' stage C, the DNA patterns were determined in multiple samples of the primary tumours and in all detected lymph node metastases. Single-cell microspectrophotometry on Feulgen-stained smears of fine-needle aspirates was used. When the most aggressive DNA pattern was considered representative, 12 primary tumours (67%) were designated as aneuploid. The frequency of aneuploidy among the metastases was almost the same (63%). In 15 cases (83%) the DNA patterns displayed by the metastatic lymph nodes were also found in the corresponding primary tumour, while in the remaining three cases (17%) the DNA pattern in the lymph node metastases was not seen in any of the multiple samples from the primary tumour. The observed tumour DNA heterogeneity may reflect either the multicellular origin of the tumour cells or the continuous evolution and progression of a neoplasm of unicellular origin, and may partly explain the dissimilarities between the DNA patterns of the primary tumour and the lymph node metastases. Biopsy samples from a number of metastatic lymph nodes are therefore required to ensure representativeness and to permit an adequate analysis of the prognostic role of the DNA ploidy status in lymph node metastases from colorectal cancer.