Molecular and cellular biology of pre-malignancy in the gastrointestinal tract

Knowledge of the anatomical polyp location might bias the pathological classification of histologically equivocal colorectal serrated polyps - a consensus study performed by pathology trainees

Colorectal serrated polyps (CSPs) comprise hyperplastic polyps (HPs), traditional (TSAs) and sessile (SSAs) serrated adenomas, as well as inflammatory cloacogenic polyps (ICPs). These lesions have typical anatomical locations and share a histomorphological overlap. In this study, we assessed the so far neglected issue as to what extent the histological classification of these lesions performed by pathology trainees is biased by the pathologists' knowledge of the polyp location in dependency on the duration of their training. To reach this aim, 49 CSPs were classified by three pathology trainees blinded to clinical data. In a second round of examination, the same raters were provided with the polyp location. A third round was conducted after a consensus conference. Intra- and inter-rater analyses were performed using Kappa (K) statistics and Spearman correlations. Our data suggest that the histological classification of CSPs performed by pathology trainees might be influenced in a clinically significant fashion by knowledge of the anatomical polyp location depending on the duration of their pathology training.

N-myc alters the fate of preneoplastic cells in a mouse model of medulloblastoma

Studying the early stages of cancer can provide important insight into the molecular basis of the disease. We identified a preneoplastic stage in the patched (ptc) mutant mouse, a model for the brain tumor medulloblastoma. Preneoplastic cells (PNCs) are found in most ptc mutants during early adulthood, but only 15% of these animals develop tumors. Although PNCs are found in mice that develop tumors, the ability of PNCs to give rise to tumors has never been demonstrated directly, and the fate of cells that do not form tumors remains unknown. Using genetic fate mapping and orthotopic transplantation, we provide definitive evidence that PNCs give rise to tumors, and show that the predominant fate of PNCs that do not form tumors is differentiation. Moreover, we show that N-myc, a gene commonly amplified in medulloblastoma, can dramatically alter the fate of PNCs, preventing differentiation and driving progression to tumors. Importantly, N-myc allows PNCs to grow independently of hedgehog signaling, making the resulting tumors resistant to hedgehog antagonists. These studies provide the first direct evidence that PNCs can give rise to tumors, and demonstrate that identification of genetic changes that promote tumor progression is critical for designing effective therapies for cancer.

Sessile serrated adenoma: challenging discrimination from other serrated colonic polyps

Sessile serrated adenoma (SSA) is the proposed precursor for microsatellite unstable colorectal carcinomas and some authorities recommend that SSAs should be managed similar to adenomas. The aim of our study was to determine whether serrated polyps can be classified with sufficient consistency to support current treatment recommendations. One hundred eighty-five serrated polyps were classified as hyperplastic polyp (HP), SSA, or traditional serrated adenoma (TSA) by 5 pathologists blinded to clinical data. The observers documented which histologic features they considered most helpful in reaching their diagnosis in each case. In a second round, the observers were provided with polyp site and size. After reaching a consensus on minimum criteria for SSA and TSA, the pathologists classified another set of 50 polyps. The interobserver concordance was calculated using kappa statistics. In the first round, the overall interobserver agreement was moderate (kappa=0.55). Concordance for HP and SSA was moderate whereas it was nearly perfect for TSA. In the second round, there was no improvement in the concordance. All observers relied more often on architectural features than on cytologic ones to distinguish SSA from HP and agreement was reached that architectural features should provide the basis for the diagnosis of SSA. Subsequently, interobserver concordance was slightly improved but remained moderate (kappa=0.58). Interobserver agreement for the diagnosis of serrated polyps is moderate. However, this level of variability is acceptable because the presence of SSA indicates increased risk of developing additional serrated polyps and carcinoma, and surveillance is appropriate.

Hyperplastic polyposis and the risk of colorectal cancer

PURPOSE

Hyperplastic polyps are usually considered to be an innocent finding with little or no potential to progress to colorectal cancer. However, recent literature suggests that some of these polyps may be morphologically and genetically distinct and lead to microsatellite unstable colorectal cancers. The purpose of this study was to define the cancer risk associated with hyperplastic polyposis.

METHODS

All patients with hyperplastic polyposis diagnosed by a single colorectal surgeon at a university hospital were followed prospectively. The diagnosis of hyperplastic polyposis was made by the presence of more than 20 hyperplastic polyps distributed throughout the colon and/or a hyperplastic polyp at least 1 cm in size in diameter in the right colon. Patient demographics, family history, size, location, and distribution of polyps and the development of colorectal cancer were noted.

RESULTS

Thirteen patients who met the criteria for hyperplastic polyposis were identified and followed prospectively. All of these patients had at least 30 polyps distributed throughout the colon, often > 100. Nine of 13 also had a hyperplastic polyp at least 1 cm in size, usually in the right colon. Of particular note, 7 of 13 patients (54 percent) were diagnosed with colorectal cancer during the study period. Four had cancer on initial diagnosis and three patients developed cancer despite frequent colonoscopic surveillance. Five of seven colorectal cancers were located in the right colon.

CONCLUSIONS

Patients with hyperplastic polyposis are at high risk for colorectal cancer. Failure to identify this subset of patients could have dire consequences.

p53 protein accumulation in colorectal cancer tissue has prognostic value only in left-sided colon tumours

The aim of this paper is to describe the prospective 10-year follow-up study of prognostic value of p53 protein accumulation in cancer cells in relation to the localisation of tumour in colorectum.

METHODS

The p53 protein accumulation has been assessed immunohistochemically in tumour tissue samples obtained from 80 selected sporadic colorectal cancer patients.

RESULTS

p53 protein accumulation was detected more often in rectum than in colon tumours. Lower survival rates were observed in patients with p53 protein accumulation in cancer cells independent of primary tumour site. Significantly lower cumulative survival rate was detected in the group of patients with left-sided colon cancer. The p53 protein accumulation was an independent prognostic factor in the left-sided colon tumours.

CONCLUSIONS

The right-sided colon tumours may be developed in p53-independent manner and p53 protein accumulation in cancer cells has prognostic value only in the left-sided colorectal tumours.

The early diagnosis and prevention of gastrointestinal cancer: problems and promises

Early detection and prevention of gastrointestinal cancer involves screening and surveillance. The efficacy of early detection tests should be subjected to well-designed studies. Clinical recommendation should be made after evaluation of new therapeutic approaches that will be based on our understanding of the molecular and cellular biology and the genetics of gastrointestinal premalignancy and cancer. Chemoprotection and alterations in diet and environment are areas that offer much promise and require clinical evaluation.