Polyps of the large intestine

Why there are polyps of the large intestine, as well as tumors in general, is still unknown.

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

Among epithelial tumors of the large intestine, which constitute the vast majority of all its tumors, distinguish adenoma and adenomatosis.

Adenoma is a benign tumor from the glandular epithelium on a pedicle or on a broad base, which has the appearance of a polyp. Histologically, there are 3 types of adenomas: tubular, villous and tubulo-villous.

The tubular adenoma (adenomatous polyp) consists mainly of branching tubular structures surrounded by a loose connective tissue. The tumor usually has a small size (up to 1 cm), a smooth surface, located on the stem, easily movable. The nasal adenoma is represented by narrow high or wide and short finger-like outgrowths of the connective tissue plate, which reach the muscular plate of the mucosa; these outgrowths are covered with epithelium. The tumor has a lobed surface, sometimes resembles a raspberry berry, is often located on a wide base and has a large size (2-5 cm). Tubulo-villous adenoma in size, appearance and histological structure occupies an intermediate position between the tubular and villous.

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

Moderate dysplasia occupies an intermediate position. In assessing the degree of severity of dysplasia, the main signs should be considered the index of multichannel number and the size of the nuclei.

Against the background of severe dysplasia in adenomas, there may be areas of glandular proliferation with pronounced signs of cellular atypism, the formation of solid structures, but without signs of invasion. Such foci are called noninvasive cancer, i.e. Carcinoma in situ. The basis for the diagnosis of noninvasive cancer is the study of a series of preparations from the whole remote polyp with the base of the pedicle (and not the material obtained with endoscopic biopsy), without revealing the germination of tumor cells in m. Mucosa mucosa - the main criterion for invasive cancer for the colon.

Concerning dysplasia of the intestinal epithelium, the opinion is basically the same: if mild and moderate dysplasia with carcinoma is not associated, then severe dysplasia inevitably progresses first to non-invasive, and then to invasive cancer. When the legs of the polyp are twisted, it is possible to move the glandular tissue into the submucosa. This phenomenon is called pseudocarcinomatous invasion and requires differentiation with invasive cancer.

Between different types of adenomas there is a clear relationship: most often the adenoma has a tubular structure and a small size. As the size grows and grows, the villousness increases and the malignancy index increases sharply, from 2% in tubular adenoma to 40% in villous. There are so-called flat adenomas that are not visible when you have an irrigoscopy (you need a colonoscopy with additional mucosal coloring) and go to cancer much more often.

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

Carcinoid ranks second in frequency among tumors of the colon, morphologically it is no different from small intestinal carcinoma (see above), but in the colon is less common.

Non-epithelial benign tumors of the large intestine may have the structure of leiomyomas, leiomyoblastomas, neurilemoma (schwannomas), lipomas, gem- and lymphangiomas, fibromas, etc. All of them are extremely rare, localized in any layers of the wall, but more often in the mucosa, submucosal layer and Endoscopic examination looks like polyps.

The term "polyp" is treated differently. It has long been accepted in Russian literature that epithelial growths are the true polyps, and therefore the term "polyp" (glandular polyp) and "adenoma" is often equated. In addition, a cooperated 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 nature.

However, the polyp is a collective term used to designate pathologies of various origin that rise above the surface of the mucous membrane. These formations, in addition to tumors (epithelial and non-epithelial nature), can be different in etiology and origin of tumor-like processes. These include hamartomas, in particular the Peitz-Egersa-Turen polyp and the juvenile polyp, similar in structure to similar formations in the small intestine.

Especially often in the colon, there is a hyperplastic (metaplastic) polyp. This is a non-tumor, disregenerative process that is characterized by an elongation of the epithelial tubules with a tendency to their cystic enlargement. The epithelium is high, serrated, and the number of goblet cells is reduced. In the lower third of the crypt, the epithelium is hyperplastic, but the amount of argetaffin cells does not differ from the norm.

Benign lymphoid polyp (and polyposis) is represented by a lymphoid tissue with phenomena of reactive hyperplasia in the form of a polyp, covered with a normal epithelium from the surface.

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

In addition to the separation of all the aforementioned 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 important for the clinic.

The results of the dynamic observation of patients indicate that most polyps undergo 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 fluctuate - from single 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 "polypos" is very conventional. VL Rivkin (1987) proposes the following:

• single polyps;
• multiple polyps;
• diffuse (family) polyposis.

Multiple (discrete) polyps are divided into group polyps when the polyps are located in one of the segments (segments) near each other, and scattered in the lesions of various parts of the colon. The term "diffuse polyposis" is used only in polyps of all parts of the colon. It has been established that the minimum number of polyps (with diffuse polyposis) is 4790, and the maximum is 15,300. Such a classification of polyps and polyposis has a great prognostic significance: the index of malignancy of single polyps is small, the multiplicity increases tenfold.

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Symptoms of polyps of the large intestine

For a long time, benign tumors and polyps of the colon can be asymptomatic. Only when the tumor reaches a large enough size there are symptoms of large intestine obstruction, and during the decay (necrosis) of a part of the tumor or polyp - intestinal bleeding. Polyps of the colon in more than half the cases are the cause of colon cancer. Most often there is malignization of the so-called villous polyp (papillary adenoma).

Diagnosis of polyps of the large intestine

The diagnosis of colon polyps is done with the help of a colonoscopy (with tumor biopsy or polypoid formation) and usually performed with the appearance of some symptoms or complications, as well as with the "expanded" clinical examination of certain populations with an increased risk of carcinomatosis. Often, a tumor or polyp is detected with irrigoscopy, but there are no very clear radiologic signs allowing differentiate benign tumors and polyps from a malignant tumor.

Differential diagnosis of large intestine polyps is carried out with malignant tumors, congenital polyposis of the digestive tract. Indirect signs of a malignant tumor (or malignancy of benign) are unexplained by other causes the occurrence of anorexia (usually with aversion to meat food), weight loss, acceleration of ESR.

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

[6], [7], [8], [9], [10], [11]

Treatment of colon polyps

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