Normal histology of the colon

Colonic melanoma, primary or regressed primary

Primary melanoma originating in the gastrointestinal tract is very rare and the majority of these tumors arise in the mucosa of the anus or rectum. A case of solitary colonic melanoma in a 79-year-old man is described with a review of pertinent literature. The surgically excised neoplasm was evaluated by routine histology and immunohistochemistry stains. Pathologic examination of the excised cecal mass revealed an 8 x 5-cm tan-pink mass with a central green-black necrotic area. Histologically, there were solid sheets of S100- and HMB-45-positive pigmented cells extending from the mucosal ulcerated surface through the bowel wall. The patient had no evidence of cutaneous or ocular primary melanoma. He remained free of recurrent disease 5 years after surgical resection of the colonic melanoma. The unique pathologic features and clinical outcome support the diagnosis of primary colonic melanoma in this patient.

The importance of clinicopathological correlation in the diagnosis of inflammatory conditions of the colon: histological patterns with clinical implications

Histological reaction patterns within the colon are not disease-specific but reflect mechanisms of injury and duration of disease. By correlating these patterns with known causes of colonic inflammation, we provide guidelines to enhance the diagnostic value of colonoscopic samples. Normal histological features are reviewed, and the sequence of inflammation and repair is used as the basis for appreciating pathological deviations. The common histological patterns of acute colitis with and without features of pseudomembranous or ischemic colitis and the morphological features of chronic colitis with and without crypt destruction are collated with clinical and endoscopic features to emphasize the importance of dialogue between the pathologist and gastroenterologist. Less common patterns, including eosinophilic colitis, graft-versus-host disease, chronic mucosal prolapse, portal hypertensive colopathy, and nonspecific or idiopathic ulcer, illustrate variations in the basic reaction patterns. Difficulties in differential diagnosis are underscored, and biopsy strategies are suggested.

Aberrant crypt foci in colorectal carcinogenesis. Cell and crypt dynamics

Aberrant crypt foci (ACF) have been identified on the colonic mucosal surface of rodents treated with colon carcinogens and of humans after methylene-blue staining and observation under a light microscope. Several lines of evidence strongly suggest that ACF with certain morphological, histological, cell kinetics, and genetic features are precursor lesions of colon cancer both in rodents and in humans. Thus, ACF represent the earliest step in colorectal carcinogenesis. This paper has the main purpose of reviewing the evidence supporting this view, with particular emphasis on cell and crypt dynamics in ACF. ACF have been used as intermediate biomarkers of cancer development in animal studies aimed at the identification of colon carcinogens and chemopreventive agents. Recently, evidence has also shown that ACF can be effectively employed in chemopreventive studies also in humans.

Non-polypoid adenomas of the colon are associated with subjacent lymphoid nodules. An experimental study in rats

BACKGROUND

Subjacent lymphoid nodules (SLNs) have been found in 38% of non-polypoid colonic adenomas in humans. In the present work the presence of SLNs in experimentally induced colonic adenomas was investigated in rats.

METHODS

1,2-Dimethylhydrazine was injected subcutaneously in 290 Sprague-Dawley rats for 27 weeks.

RESULTS

An SLN was present in 28.6% of the 84 adenomas, in 8.4% of the 119 adenocarcinomas, and in 9.7% of the 31 small carcinomas without remnant adenomatous tissue. An SLN was found in 35.6% of the 59 non-polypoid neoplasias but only in 9.1% of the 175 polypoid (that is, exophytic) neoplasias. When only adenomas were considered, SLNs were present in 50.0% of the 34 non-polypoid adenomas but only in 14.0% of the 50 polypoid adenomas.

CONCLUSIONS

Non-polypoid colonic adenomas evolve preferentially from the minimal fraction of the colonic mucosa that overlays the few existing lymphoid nodules in rats.

Biopsy diagnosis of colitis: possibilities and pitfalls

The histopathologic diagnosis of inflammation is common in colorectal biopsies but is of limited value, if not further specified. We reviewed 280 endoscopic colorectal biopsy specimens for nonneoplastic disease from 100 consecutive patients in order to assess (a) the frequency of inflammation in excess of the physiologic infiltrate, (b) the frequency with which the cause of the inflammation could be specified, and (c) the interobserver variability in diagnosing inflammation. Based on the reviewers' impression, each case was classified into one of three categories: (I) normal or nonspecific change, (II) nonspecific inflammation, and (III) inflammation suggestive or diagnostic of specific cause. Inflammation was diagnosed in 68% of cases. The majority of these cases (75%) showed features typically associated with specific types of colitis, including Crohn's disease (n = 16), ulcerative colitis (n = 13), inflammatory bowel disease not otherwise specified (n = 5), infectious colitis (n = 6), ischemic colitis (n = 4), solitary rectal ulcer syndrome (n = 3), radiation colitis (n = 2), and lymphocytic colitis (n = 2). Interobserver variability was greatest in biopsy specimens interpreted by the reviewers as normal or showing nonspecific changes, most of which had been diagnosed as mild inflammation by the original pathologists. Etiologic classification of colitis was lacking in 59% of the cases interpreted by the reviewers as suggestive or diagnostic of a specific cause. We conclude that (a) the majority of colorectal biopsy specimens from patients with nonneoplastic disease in this series show inflammation, (b) the majority of such cases allow a specific cause of colitis to be suggested or firmly diagnosed, and (c) pathologists tend to overdiagnose the physiologic inflammatory infiltrate as evidence of colitis and underdiagnose specific etiologic types of colitis.

Management of dysplasia in the columnar-lined esophagus

The management of patients with high-grade dysplasia in Barrett's esophagus is complex and controversial with regard to electing continued endoscopic biopsy surveillance until an early adenocarcinoma is detected or proceeding with partial esophagogastrectomy. Clinical recommendations to patients for either option should be individualized and based on several parameters reflecting patient and clinician factors. Available data on interpretational variation in the diagnosis of dysplasia; limitation of diagnostic errors with the use of a rigorous, systematic endoscopic biopsy protocol; new information on the apparent benign natural history of high-grade dysplasia in some patients; and the morbidity and mortality of esophageal resection all suggest that recommendation for continued endoscopic biopsy surveillance is an appropriate clinical practice in selected patients. Ongoing research investigations on high-grade dysplasia in Barrett's esophagus aim to reduce the potential for diagnostic errors, simplify cancer surveillance, and develop therapeutic interventions that are safer than but as effective as surgery.

Guidelines for the initial biopsy diagnosis of suspected chronic idiopathic inflammatory bowel disease. The British Society of Gastroenterology Initiative

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Diagnostic difficulty arising from rectal recovery in ulcerative colitis

AIMS

To ascertain whether the dogma that a normal rectal biopsy precludes a diagnosis of ulcerative colitis is correct.

METHODS

Rectal biopsy specimens from a prospective group of 24 asymptomatic patients, with an established diagnosis of ulcerative colitis, were examined in a blinded study alongside 10 normal rectal biopsy specimens from an age and sex matched patient cohort without ulcerative colitis. Each biopsy specimen was assessed by three pathologists and ascribed to one of four categories: normal; borderline abnormality (one or more minor nonspecific abnormalities which, when combined, did not fulfil the minimal acceptable criteria for a diagnosis of ulcerative colitis); minimal features of chronic ulcerative colitis; and unequivocal ulcerative colitis.

RESULTS

Two patients with ulcerative colitis had normal biopsy specimens; nine specimens were categorised as borderline abnormality, one as showing the minimal changes of chronic ulcerative colitis, and 12 as having the typical changes of chronic ulcerative colitis. Thus, 11 (46%) of the 24 patients had a rectal biopsy specimen that was devoid of the acceptable attributes on which a diagnosis is established, despite a confident previous diagnosis. Ten of these 11 cases had disease limited to the rectum. Review of all previous histological biopsy specimens (n = 164) and clinical data, including drug treatment, failed to identify any attributes that might be prognostic markers for future rectal mucosal healing.

CONCLUSIONS

A normal rectal biopsy specimen, though uncommon, may occur in longstanding colitis. Moreover, in 46% of these asymptomatic but established cases the degree of healing may preclude a diagnosis of ulcerative colitis without comprehensive clinical and radiological details. Pathologists need to be aware of this minimal end of the spectrum of disease.

Diverticular disease-associated chronic colitis

A clinical syndrome of chronic colitis unique to the sigmoid colon harboring diverticular was recently reported; its histopathological appearance has not been fully elucidated. In this study, the authors analyzed the clinical and pathological features of 23 patients (age range, 38-87 years; median age, 72 years) with diverticular disease-associated chronic colitis. Nineteen presented with hematochezia; four had abdominal pain. Colonoscopic visualization of the mucosa showed patchy or confluent granularity and friability affecting the sigmoid colon encompassing diverticular ostia. Colonic mucosae proximal and distal to the sigmoid were endoscopically normal. Mucosal biopsy specimens showed features of idiopathic inflammatory bowel disease that included plasmacellular and eosinophilic expansion of the lamina propria (100%), neutrophilic cryptitis (100%) with crypt abscesses (61%), basal lymphoid aggregates (100%), distorted crypt architecture (87%), basal plasmacytosis (61%), surface epithelial sloughing (61%), focal Paneth cell metaplasia (48%), and granulomatous cryptitis (26%). Concomitant rectal biopsies obtained in five patients demonstrated histologically normal mucosa. Fourteen patients treated with high-fiber diet or antibiotics or both improved clinically, as did nine patients administered sulfasalazine or 5-aminosalicylic acid. Five patients underwent sigmoid colonic resection, three for stricture with obstruction and two for chronic blood loss anemia. Among a control population of 23 age- and gender-matched patients with diverticular disease without luminal surface mucosal abnormality, none required resection during the same follow-up period. By Fisher's exact test, a statistically significant difference in outcome for patients with and without colitis was detected (p = 0.049). In addition, three patients developed ulcerative proctosigmoiditis 6, 9, and 17 months after the onset of diverticular disease-associted colitis. The data indicate that diverticular disease-associated chronic sigmoid colitis expresses morphological features traditionally reserved for idiopathic inflammatory bowel disease. Its clinical and endoscopic profiles permit distinction from Crohn's disease and ulcerative colitis. Patients with chronic colitis in conjunction with diverticula are at increased risk for sigmoid colonic resection. Diverticular disease-associated chronic colitis may also precede the onset of conventional ulcerative proctosigmoiditis in some cases.

Interpretation of large intestinal mucosal biopsy specimens

The development of flexible endoscopes has led to a great increase in the examination and mucosal biopsy evaluation of all portions of the large intestine and rectum. Examinations are now performed not only for the determination of diagnosis but also for the monitoring of the course of a wide variety of conditions and for the early detection of complications. This review concentrates on the uses and interpretations of such biopsies in a large number of inflammatory conditions, with special emphasis on the correlations with clinical and functional features. Illustrated are examples of infections, idiopathic inflammatory bowel disease (IBD), vascular disorders, motor and mechanical conditions, toxic and physical reactions, and other inflammatory conditions. Mucosal biopsy specimens also are obtained to identify dysplasia and to evaluate mass lesions, and these subjects are well covered in other articles within this symposium. In patients with chronic disorders multiple examinations are now expected to follow the course of the disease and to detect and correct any complications at an early stage. The exact reasons for the endoscopy and relevant clinical data are essential for the optimal analysis of these mucosal biopsy specimens.

Morphometric discrimination of colonic tubular adenoma from adenocarcinoma by vector and tensor analyses

Four parameters were considered in this study to discriminate between tubular adenoma and adenocarcinoma of the colon. The deformation of the tubular profile (TD) and the average sector resultant (AR) were used as supracellular parameters, the vector resultant strain (VS) which represented the cellular crowding as a cellular parameter, and the deformation of the nucleus (ND) as a nuclear parameter. Statistical comparison between the two groups showed that all the parameters had high levels of significance. Direct discriminant analysis was applied to discriminate between the two diseases and all parameters showed large F-ratios; however, the evaluation by the stepwise discriminant method indicated that ND had a sufficient power of discrimination between the two diseases. Biplot with confidence interval ellipses (95%) was plotted for ND versus TD to demonstrate the graphical separation of the groups.

Major histocompatibility class II expression on the small intestinal nervous system in Crohn's disease

Widespread alterations of the gut autonomic nervous system have been described in Crohn's disease. Immunohistochemistry shows that these alterations are associated with the expression of major histocompatibility (MHC) class II antigens (HLA-DR) on enteroglial cells in the ganglia of the submucous and myenteric plexuses and on the enteroglial sheaths of the nerve extensions. Neuronal cell bodies and extensions do not express MHC class II antigens. The class II expression is associated with the presence of UCHL1-positive T lymphocytes. MHC class II expression can also be found on endothelial cells and vascular smooth muscle cells but not on smooth muscle cells of the muscularis mucosae or propria. The intensity of MHC class II expression on the glial cells of the enteric nervous plexus and on endothelial cells correlates well with the intensity of class II expression on epithelial cells.

Vectorial release of carcinoembryonic antigen induced by IFN-gamma in human colon cancer cells cultured in serum-free medium

Confluent monolayers of intestinal cell lines are useful models for studies of intestinal epithelial structure and function. Three cell lines have retained morphological and functional properties of intestinal epithelial cells compatible with such studies: Caco-2, T84 and HT29. However, the requirement of fetal bovine serum for the culture of these cells does not facilitate the design of experiments dealing with growth factors or hormonal regulation. The clonal intestinal cell line HT29-D4 can be cultured as fully differentiated epithelial monolayers in a synthetic medium containing transferrin, selenous acid, epidermal growth factor and suramin, a potent differentiation inducer. In the present study it is shown that HT29-D4 cells grown on permeable substratum in this synthetic medium developed electrically active monolayers consisting of columnar cells with morphological characteristics of normal enterocytes. After metabolic labelling with [35S]-methionine, HT29-D4 monolayers released most of their radiolabelled secretory proteins preferentially in the basal compartment of the cell culture chamber. However, the carcinoembryonic antigen, shown to be present in the apical plasma membrane, was exclusively released apically. This oriented release was stimulated by recombinant gamma-interferon (IFN-gamma) added only in the basal chamber, suggesting a basolateral restriction for IFN-gamma receptors.

Endoscopic biopsy technique for acquiring larger mucosal samples

Biopsies of the esophagus, stomach, and intestine are most often obtained using the traditional advance-and-close method with flexible endoscopes by extending an open forceps several millimeters beyond the endoscope tip to sample the mucosa, all under direct vision. We developed an alternative "turn-and-suction" endoscopic biopsy technique that permits the acquisition of larger mucosal samples. The biopsy forceps is advanced into the lumen, opened, and withdrawn backward until it is flush with the endoscope tip. Next, the endoscope tip is turned gently into the wall while air is suctioned from the lumen, and the biopsy forceps is very slightly advanced and then closed, usually without direct visualization. After straightening the endoscope tip, the biopsy is obtained by withdrawing the forceps and avulsing a superficial mucosal sample. By using this new method, we have safely taken over 10,000 biopsies without complications in endoscopic surveillance research protocols in patients at risk for gastrointestinal cancer. To compare the sizes of biopsies obtained with these two techniques, histologic sections of 341 mucosal samples from 12 patients with chronic ulcerative colitis were studied retrospectively. The mean greatest length of biopsy sections using the traditional technique was 4.72 mm, and using our new technique was 7.35 mm (56% longer). The turn-and-suction endoscopic biopsy method is best applied when flat mucosa is randomly sampled to seek microscopic pathologic changes that are not visible endoscopically, and may be advantageous for various non-histologic research analyses of gastrointestinal mucosa which are limited by tissue quantity.

Ultrastructural and cytoarchitectural features of lymphoreticular organs in the colon and rectum of adult BALB/c mice

The structure and function of colonic mucosal lymphoid organs remain largely unexplored, especially in the rectum hidden within the pelvic vault. Two-month-old female BALB/c mice were anesthetized, and the entire colon was removed from cecum to anus. Distal colonic patches were then prepared for electron microscopy or were quick-frozen and sectioned for immunoperoxidase localization of B cells and T cell subsets. Aggregated lymphoid follicles were distributed irregularly along the entire colon with an average of 1.4 patches per centimeter of colon length. There were large collections of follicles opposite the ileocecal valve (cecal patches), variable numbers of patches throughout the colon, and at least one patch within 10 mm of the anus (rectal patch). Follicles were adjacent to branching crypts lined by epithelium infiltrated by lymphoid cells and containing few goblet cells. In electron micrographs, M cells were identified by their short, irregular microvilli; intraepithelial lymphoid cells; reduced lysosomal dense bodies; and an expanded tubulovesicular network. Small germinal centers were seen. Cytoarchitectural components of colonic lymphoid follicles and Peyer's patch follicles were remarkably similar, despite differences in surrounding mucosa and luminal microbial exposure. The presence of organized lymphoid tissue with M cells and germinal centers suggests that transepithelial particle transport and antigen recognition can take place in the rectum. Whether such tissue has the capacity for uptake of luminal microorganisms is of particular interest, not only because colonic follicles may be sites for local initiation of immune responses but also because they may be important entry points for systemic infection.