Polyps of the large intestine

Why colon polyps, like tumors in general, occur is still unknown.

Benign tumors, according to the International Histological Classification of Intestinal Tumours of the WHO (No. 15, Geneva, 1981), are divided into 3 groups: epithelial tumors, carcinoid and non-epithelial tumors.

Among the epithelial tumors of the colon, which make up the vast majority of all its tumors, a distinction is made between adenoma and adenomatosis.

Adenoma is a benign tumor of glandular epithelium on a stalk or on a broad base, having the appearance of a polyp. Histologically, there are 3 types of adenomas: tubular, villous and tubulovillous.

Tubular adenoma (adenomatous polyp) consists mainly of branching tubular structures surrounded by loose connective tissue. The tumor is usually small (up to 1 cm), has a smooth surface, is located on a stalk, and is easily mobile. Villous adenoma is represented by narrow, high or wide and short finger-shaped outgrowths of the connective tissue lamina propria, which reach the muscularis mucosa; these outgrowths are covered with epithelium. The tumor has a lobular surface, sometimes resembles a raspberry, is often located on a wide base and is large (2-5 cm). Tubulovillous adenoma occupies an intermediate position between tubular and villous adenoma in terms of size, appearance, and histological structure.

In all three types of adenomas, the degree of morphological differentiation and dysplasia is taken into account - weak, moderate and severe. With weak dysplasia, the architecture of the glands and villi is preserved, they contain a large amount of mucous secretion, the number of goblet cells is slightly reduced. The cells are usually narrow, their nuclei are elongated, slightly enlarged; mitoses are single. With severe dysplasia, the structure of the glands and villi is grossly disrupted, there is no secretion in them. Goblet cells are single or absent, there are no enterocytes with acidophilic granules (Paneth cells). The nuclei of the colonocytes are polymorphic, some of them are shifted to the apical side (pseudomulteriate), numerous mitoses are visible, including pathological ones.

Moderate dysplasia occupies an intermediate position. In assessing the severity of dysplasia, the main signs should be considered the index of multi-row and the size of the nuclei.

Against the background of severe dysplasia, areas of glandular proliferation with pronounced signs of cellular atypism, the formation of solid structures, but without signs of invasion may be encountered in adenomas. Such foci are called non-invasive cancer, i.e. carcinoma in situ. The basis for diagnosing non-invasive cancer is the study of a series of preparations from a completely removed polyp with the base of the stalk (and not material obtained during endoscopic biopsy), while no tumor cell invasion into m. mucosa of the mucous membrane was detected - the main criterion for invasive cancer for the colon.

Regarding intestinal epithelial dysplasia, the opinion is generally unanimous: if mild and moderate dysplasia are not associated with carcinoma, then severe dysplasia inevitably progresses first to noninvasive and then to invasive cancer. When the polyp stalk is twisted, glandular tissue may migrate to the submucosal layer. This phenomenon is called pseudocarcinomatous invasion and requires differentiation from invasive cancer.

There is a clear relationship between different types of adenomas: most often, an adenoma initially has a tubular structure and a small size. As it grows and increases in size, villosity increases and the malignancy index increases sharply - from 2%in tubular adenoma up to 40% in villous. There are so-called flat adenomas, which are not visible during irrigoscopy (colonoscopy with additional staining of the mucous membrane is required) and much more often develop into cancer.

If multiple adenomas are found in the colon, but not less than 100, then, according to the International Histological Classification of WHO, this process should be classified as adenomatosis. If their number is smaller, we can talk about multiple adenomas. With adenomatosis, usually all adenomas have a predominantly tubular structure, much less often - villous and tubulovillous. The degree of dysplasia can be any.

Carcinoid is the second most common tumor of the colon; morphologically, it is no different from carcinoid of the small intestine (see above), but is less common in the colon.

Nonepithelial benign tumors of the colon can have the structure of leiomyoma, leiomyoblastoma, neurilemoma (schwannoma), lipoma, hem- and lymphangiomas, fibromas, etc. All of them are extremely rare, localized in any layers of the wall, but more often in the mucous membrane, submucous layer and during endoscopic examination look like polyps.

The term "polyp" is interpreted in different ways. In domestic literature, it has long been accepted that true polyps are epithelial growths, therefore, the concepts "polyp" (glandular polyp) and "adenoma" are often equated. In addition, a cooperative study of the frequency and nature of various colon diseases in large specialized clinics showed that the overwhelming majority of polyps (92.1%) are tumors of epithelial origin.

However, polyp is a collective term used to designate pathological formations of various origins that rise above the surface of the mucous membrane. These formations, in addition to tumors (epithelial and non-epithelial nature), can be tumor-like processes of various etiologies and origins. These include hamartomas, in particular the Peutz-Jeghers-Touraine polyp and juvenile polyp, similar in structure to similar formations in the small intestine.

Hyperplastic (metaplastic) polyp is especially common in the colon. This is a non-neoplastic, dysregenerative process, which is characterized by the elongation of epithelial tubes with a tendency to their cystic expansion. The epithelium is high, serrate-twisted, the number of goblet cells is reduced. In the lower third of the crypts, the epithelium is hyperplastic, but the number of argentaffin cells does not differ from the norm.

A benign lymphoid polyp (and polyposis) is represented by lymphoid tissue with reactive hyperplasia in the form of a polyp covered on the surface by normal epithelium.

An inflammatory polyp is a nodular polypoid formation with inflammatory infiltration of the stroma, covered by normal or regenerating epithelium, often ulcerated.

In addition to dividing all the above polyps by etiology and histological structure, the size of the polyps, the presence and nature of the polyp stalk, and finally, the number of polyps are of great clinical importance.

The results of dynamic observation of patients indicate that the majority of polyps go through stages from small to large, from mild dysplasia to severe, up to the transition to invasive cancer.

The number of polyps in one patient can vary from a few to several hundred or even thousands. In the presence of 20 or more polyps, the term "polyposis" is used, although the boundary between the concepts of "multiple polyps" and "polyposis" is very arbitrary. V. L. Rivkin (1987) suggests distinguishing:

• solitary polyps;
• multiple polyps;
• diffuse (familial) polyposis.

Multiple (discrete) polyps are divided into grouped, when polyps are located in one of the sections (segments) close to each other, and scattered, when different sections of the colon are affected. The term "diffuse polyposis" is used only when polyps affect all sections of the colon. It has been established that the minimum number of polyps (in diffuse polyposis) is 4790, and the maximum is 15,300. Such classification of polyps and polyposis has great prognostic value: the malignancy index of single polyps is small, while that of multiple polyps increases tens of times.

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Symptoms of Colon Polyps

Benign tumors and polyps of the colon may be asymptomatic for a long time. Only when the tumor reaches a sufficiently large size do symptoms of colon obstruction appear, and when part of the tumor or polyp disintegrates (necrosis) - intestinal bleeding. Colon polyps are the cause of colon cancer in more than half of cases. Most often, malignancy of the so-called villous polyp (papillary adenoma) appears.

Diagnosis of colon polyps

The diagnosis of "colonic polyps" is made by colonoscopy (with biopsy of the tumor or polyp-like formation) and is usually carried out when some symptoms or complications arise, as well as during "extended" medical examination of certain groups of the population with an increased risk of carcinomatosis. Often, a tumor or polyp is detected by irrigoscopy, but there are no very clear radiographic signs that allow differentiating benign tumors and polyps from malignant tumors.

Differential diagnostics of colon polyps is carried out with malignant tumors, congenital polyposis of the digestive tract. Indirect signs of a malignant tumor (or malignancy of a benign tumor) are the occurrence of anorexia unexplained by other reasons (usually with an aversion to meat food), weight loss, and an increase in ESR.

Finally, targeted transendoscopic biopsy followed by histological examination of the biopsy allows for a more accurate diagnosis.

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Treatment of colon polyps

Treatment of colon polyps (especially villous polyps) is most often surgical. However, small tumors and colon polyps can be removed using modern endoscopic techniques (electrocoagulation, laser coagulation, removal with a special "loop", etc.).