Intratumoral heterogeneity in colorectal carcinoma: Trucut sampling for DNA ploidy analysis

Background. Solid tumors, such as colorectal carcinomas, consist of cell su bpopulations that differ both genetically and in their clinical behavior. M any authors have examined cell kinetics and DIVA content in colorectal tumo rs in correlation to clinical and pathological variables with different res ults. The interpretation of those results present some difficulties related to tumor heterogeneity that to date ale unsolved. Our study is based on a new method of colon cancer sampling for DNA content determination. The aim of this work was to reduce the risk of incorrect DNA evaluation due to tumo r heterogeneity. Material and Methods. Our study was based on eleven select ed cases of T3 colorectal carcinoma. Flesh surgical specimens from the prim ary tumor site were taken during surgery. For each case at least four sampl es were taken using a 23 gauge trucut from the outside of the serosa throug h the tumor. to the lumen of the colon. The specimens were stained accordin g to a modified Feulgen method and DNA content was measured by image analys is. Three parameters were evaluated: DNA index, ploidy and proliferation le vel (considered as the sum of elements corresponding to the S and G2 phases ). Results. One of the eleven (9.1%) tumors showed a diploid pattern; four out of eleven (36.4%) cases showed a tetra/polyploid partten and six out of eleven (54.5%) cases showed an aneuploid pattern. Three tumors were monocl onal (27.3%), one diploid and two aneuploid. Eight were polyclonal (72.7%). Considering the single specimen, seven out of sixty-eight specimens (10.3% ) were inadequate because of scanty material. Twenty-five out of the sixty- one adequate specimens (41%) were monoclonal and thirty-six (59%) were poly clonal. Five tumors (three monoclonal and two polyclonal) showed the same c ell clones on all the examined samples. The remaining six tumors showed int er-regional variability. In six of the eight polyclonal cases (75%) multipl e stem lines were evident, analyzing only one sample taken close to colon s ei osa, while in one case (25%) it was necessary to examine two samples in order to see the polyclonality of the lesion. When samples taken close to m ucosa where analyzed however; one sample was not enough to show tumor polyc lonality in five of the eight polyclonal examined cases. Proliferation leve l varied greatly in different parts of the same carcinoma and did not corre late to the site from which the sample was taken. Conclusion. In the presen t study, we demonstrated that DNA ploidy differences may exist between the superficial and the deep part of the same neoplasia and that tumor samples show a greater variability in the deeper layers. Using trucut samplings, it was possible to point out the majority of aneuploid cell populations close to the serosa. In conclusion, trucut biopsy permits full thickness samplin g of the tumoral mass and allows, from few samples, to evaluate the multipl e DNA stemlines present in different parts of a colorectal tumor.