Intratumor genetic heterogeneity in advanced human colorectal adenocarcinoma.

Colorectal carcinogenesis is widely accepted as one of the best-characterized examples of stepwise progression. The existing colorectal carcinogenesis model assumes genetic homogeneity of individual tumors for the main known genetic alterations: K-ras and p53 genes point mutations and loss of heterozygosity (LOH) of chromosome 5q and 18q. The object of the present study was to demonstrate the existence of an intratumor genetic heterogeneity in advanced sporadic colorectal carcinoma for these genetic alterations. Using improved tissue microdissection and DNA extraction, for each tumor, amplifiable DNA was obtained from 15 to 20 areas, of which 1 to 2 concerned lymph node metastases (LNM). This study revealed that 10 of 15 (67%) analyzed tumors were heterogeneous for at least 1 genetic alteration, with between 2 and 6 genotypically different clones detected per tumor. No correlation was observed between the genotype of these subclones and histological differentiation or invasive propensity. Intratumor heterogeneity was more frequently observed for LOH than for point mutations, 67% and 58% for LOH at APC and DCC locus, and 20% for mutation of either the K-ras or p53 gene. In 5 of the 9 (56%) heterogeneous cases with available LNM, the genotype observed in the LNM was different from that of the main clone in the primary tumor, and moreover, 2 of the LNM displayed a genotype undetected in the primary tumor. In conclusion, intratumor genetic heterogeneity was demonstrated in advanced sporadic colorectal carcinoma and was represented as topographically distinct genotypic subclones. Taking into account such a significant genetic heterogeneity of colorectal tumors, the use of genetic markers for prognosis management should be reconsidered.

Expression of telomerase genes correlates with telomerase activity in human colorectal carcinogenesis.

The human telomerase enzyme is composed of two essential components, hTR, which acts as a template for reverse transcription, and hTERT, which is the putative catalytic subunit for the enzyme. Recent studies have demonstrated a good correlation between hTERT expression and telomerase activation, whereas RT-PCR results seemed to reveal that hTR is ubiquitously expressed in all cells. These observations left unclear the role of hTR, and to a lesser extent hTERT, in the regulation of telomerase activation. In the present study, the correlation of telomerase activity and the expression of these genes was examined in a total of 70 colorectal tissues (25 adenocarcinomas, 30 adenomas, and 15 samples of normal colorectal mucosa). Total RNA for RT-PCR analysis and cell extracts for TRAP assay were obtained from consecutive sections and histological control was simultaneously performed. To avoid false-positive results, due to the fact that hTR cDNA and genomic hTR DNA are identical (the gene has no introns), extensive DNase digestion was performed before cDNA synthesis. RT-PCR analysis revealed that hTERT mRNA was expressed in all cancers and in 13 of 14 telomerase-positive adenomas, but never in telomerase-negative colorectal tissues. hTR transcripts were observed in all telomerase-positive samples but also in three telomerase-negative samples, two adenomas, and one normal colonic mucosa. It is concluded that hTERT and hTR expression is strongly correlated with telomerase activity. hTR transcripts, however, also occur in some telomerase-negative tissues and these results are in keeping with the concept that hTERT expression is a major regulator of telomerase activity.

Telomerase activation in colorectal carcinogenesis.

Telomerase activity has been detected in germ cells as well as in the developing embryo. Activity is no longer detectable in most somatic cells of the neonate, although low levels of activity persist in regenerative tissues. Telomerase has been found to be reactivated or up-regulated in the majority of cancers. The colorectal adenoma-carcinoma sequence is one of the best-characterized models of multistep tumourigenesis and is thus suitable for determining at which stage telomerase is activated. Telomerase activity was examined by telomeric repeat amplification protocol (TRAP) assay in 96 cases of colorectal tissues, including 50 carcinomas, 31 adenomas, and 15 normal colonic tissues. For each case, histological diagnosis and telomerase activity were determined on consecutive frozen sections. In order to reduce the chance of a false-negative TRAP assay due to RNA degradation, the integrity of rRNA in the tissues was verified in each case. Twenty-five carcinomas, 30 adenomas, and all of the 15 normal colorectal mucosal samples showed no or only partial rRNA degradation and only in these cases was the TRAP assay interpreted. None of the normal tissues exhibited telomerase activity. In contrast, all of the 25 cancers and 47 per cent (14/30) of the adenomas were positive. In adenomas, telomerase activation was highly significantly related to the grade of dysplasia (p< 0.0001). All adenomas which contained high-grade dysplasia revealed telomerase activity, whereas telomerase activity was detectable in only 20 per cent (4/20) of cases with exclusively low-grade dysplasia. These results indicate that telomerase activation, which may be an obligatory step in colorectal carcinogenesis, occurs in the progression from low-grade to high-grade dysplasia in adenomas. Furthermore, in the adenoma-carcinoma sequence, telomerase activation seems to occur later than K- ras mutation but earlier than p53 mutation.

Digestive leishmaniasis in acquired immunodeficiency syndrome: a light and electron microscopic study of two cases.

An increased incidence of visceral leishmaniasis in patients infected with the human immunodeficiency virus (HIV) is observed in areas in which both infectious diseases are endemic. Intensive worldwide traveling has also resulted recently in an increasing number of leishmanial and HIV coinfections in nonendemic areas. We describe the clinical, light microscopic, and ultrastructural features of two cases of imported, HIV-related, visceral leishmaniasis involving the alimentary tract, including the esophagus, the stomach, the duodenum, the ileum, the colon, and the rectum. We also discuss the differentiation of leishmanial infections from other HIV-related gastrointestinal opportunistic infections.

Expression of p53 protein in gastric carcinomas. Association with histologic type and prognosis.

We searched for p53 protein accumulation in 72 gastric carcinomas. Of the 38 cases of the diffuse type, only four were positive for p53. Of the 34 cases of intestinal type, 24 had p53 protein accumulation. This difference (p < 0.0001) between histological types was present regardless of whether the carcinoma was superficial or infiltrative. Normal epithelial cells and intestinal metaplasia were never positive. No correlation was found between p53 protein accumulation and tumor size, lymph node metastases, age or sex of the patients. Although tumor size, lymph node metastases, and infiltrative character all have prognostic value, p53, either alone or in association with these parameters, does not; p53 mutations seem to play a role in oncogenesis only in the intestinal type of gastric carcinomas; however, p53 protein accumulation has no prognostic value in gastric tumors.

[Segmental ischemic colitis in lymphocytic thrombotic venulitis]. / Colite ischémique segmentaire sur veinulite lymphocytaire thrombosante.

This case illustrates the difficulty of diagnosing a colonic stenosis of ischemic origin. A 70-year-old lady presents with abdominal pain, fever and melaena. Lc are 15.2, ESR 39 mm, CEA 2.7 ng/ml. A barium enema shows a stenosis of the transverse colon that is suspicious of neoplasia. At time of operation, an induration of the transverse colon is found with edema of the corresponding mesocolon but no tumour is palpated. A resection of this area is performed and an end to end anastomosis performed. Pathology shows an ischemic colitis secondary to a lymphocytic thrombotic venulitis. The patient is discharged home one month postoperatively. 4 weeks later she is readmitted with the same symptoms. A gastrograffin enema shows a similar stenosis in the transverse colon including the anastomosis. The diagnosis is made of a recurrent ischemic stenosis. The patient improves over a 10-day period of conservative treatment (anticoagulation, TPN, steroids). A control barium enema shows a near resolution of the stenosis. The majority of ischemic colitis are of arterial origin nevertheless ischemic colitis of venous origin exists. The factor causing venous ischemia are not known. It is though thought to be associated with hypersensitivity vasculitis of drug origin. Its initial diagnosis versus neoplasia is difficult but once made there is a good response to a conservative treatment.

[Eosinophilic gastroenteritis: two case reports]. / Gastro-entérite à éosinophiles: à propos de deux cas.

Eosinophilic gastroenteritis is a rare lesion that may present a diagnostic problem to the surgeon. It may be confused with a malignant tumor because it often presents with intestinal obstruction. We treated two cases at the Hôpital de zone de Morges. In one case the lesion was in the gastric antrum and in the other the ascending colon. Only 27 cases of colonic eosinophilic gastritis are described in the medical literature.

Improved method for mapping gastric intestinal metaplasia using selective histochemical morphometry.

A gastrectomy specimen containing two tubular adenomas from a 67-year-old woman was mapped by an improved method using selective histochemical staining. The specimen was divided into 83 blocks measuring 4.0 cm x 0.5 cm. Sections from the blocks were stained with alcian blue (pH 2.5) to detect mucin. Alcian blue-stained fields were easily identified and measured with the aid of a MOP 30 interactive digital image analyzer. The total area of gastric mucosa analyzed in the 83 sections measured 3,270.9 sq mm while the area occupied by alcian blue-stained goblet cells measured 755.9 sq mm (23.1% of the total area). Intestinal metaplasia was present in 46 of 83 blocks. Both the mean size of alcian blue-positive fields per section as well as the number of alcian blue-positive fields per section were significantly larger in the antral zone I and the intermediate zone II than in the fundal zones III, IV and V. The highest proportion of gastric mucosa with intestinal metaplasia was not found around the two gastric adenomas, but elsewhere. There was no significant difference in the proportion of intestinal metaplasia between the greater and lesser curvatures, further challenging the belief that intestinal metaplasia is always greatest along the lesser curvature. The method described will permit future studies of the possible association between intestinal metaplasia and dysplasias and adenocarcinomas of the stomach.

Prognostic factors in colonic cancer.

Prognostic variables in 251 'curative' specimens of colonic cancer were studied. Subjective variables--tumour type, grade of differentiation, character of invasive margin and lymphocytic infiltration--were associated with fair to excellent levels of inter-observer agreement. Variables found to be of prognostic significance by univariate analysis were subjected to Cox regression analysis. This was undertaken for all three observers and for a consensus grading. No case in which direct spread in continuity was limited to the bowel wall was associated with a cancer-related death; 63 such specimens were removed as a group with an excellent prognosis and did not require further stratification. In the remaining 188 cases, all showing extramural spread, only lymph node invasion, character of invasive margin and tumour type were independent prognostic variables. The model differs from that developed previously for rectal cancer and is superior to the Dukes classification.

Idiopathic entero-colic lymphocytic phlebitis. A cause of ischemic intestinal necrosis.

Histological examination of the surgical specimens of three patients presenting with intestinal ischemic necrosis disclosed extensive lesions of lymphocytic phlebitis associated with thrombosis of different ages. Arterioles and arteries were not affected. The lymphocytic infiltrate was composed of a mixture of T- and B-lymphocytes. None of the patients showed clinical or laboratory evidence of systemic vasculitis. Follow-up ranged between 4 months and 5 years. There has been no recurrence necessitating reoperation. The etiology of this clinicopathological entity has not been elucidated.

Gastric dysplasia. A histological follow-up study.

To evaluate the clinical and biological significance of gastric dysplasia, we reviewed the histology of all available specimens of gastric mucosa in 85 patients in whom dysplasia had been previously diagnosed. The initial diagnosis of dysplasia was mild (Dy I) in 23 cases, moderate (Dy II) in 41 cases, and severe (Dy III) in 21 cases. The length of follow-up varied from 3 months to 11 years, with an average of 42 months. The follow-up of cases with Dy I and Dy II suggests that both lesions progress slowly and in most instances will remain stable or regress. In 18 cases, a carcinoma was found--17 in the group of Dy III and one in the group of Dy II. Of the 18 carcinomas, nine were at an early stage. Our data suggest that severe dysplasia is a reliable marker of high risk of gastric cancer and represents a strong indication for a gastrectomy.

[Tumors and myelomonocytic leukemia]. / Tumeurs et leucémie myélomonocytaire.

Extramedullary solid tumors of early granulocytic and monocytic precursors are a rare manifestation of acute non lymphoblastic leukemias. They may develop during the course, or be the presenting sign, of leukemia. We describe a case of myelomonocytic tumors involving the skin and the stomach as primary manifestations of leukemia. Two months later the patient developed acute myelomonocytic leukemia with a rapidly fatal course. At autopsy, multiple tumors were found in the skin, the peridural space, the muscles, the peritoneum, the pleura and in several organs, such as in the lungs, the kidneys, the gallbladder and in the whole gastrointestinal tract. The many synonyms of these tumors, the localisation, the chronology of the clinical manifestations and the various problems in the diagnosis are discussed. In the differential diagnosis of histiocytic lymphoma, identification of myelomonocytic differentiation in neoplastic cells should be done, using special techniques, such as immunoperoxidase and cytochemical stains for esterases.

[Histologic diagnosis of lymphoproliferative diseases of the digestive tract]. / Le diagnostic histologique des lésions lymphoprolifératives du système digestif.

The pathologic diagnosis of lymphoproliferative diseases of the gastrointestinal tract is sometimes very difficult or even impossible. In the majority of cases the gross appearance of the lesion is not helpful. Three histological criteria, when present, justify a definite diagnosis: cellular anaplasia and nodal involvement in malignant lymphomas, and the presence of germinal centers in pseudolymphomas. All other histological criteria, including transmural extension of the lesions, are of only relative diagnostic value. The definite diagnosis of these diseases is based on histological examination of the entire lesion. Only a diagnosis of probability is generally possible on endoscopic biopsies. The demonstration of different chains of immunoglobulins by means of immunohistochemistry may help in revealing malignant lymphomas with secretory activity and a polyclonal pattern in reactive lesions.