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II./2.4.: Extrauterine visceral leiomyomata
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Since smooth muscle occurs at many locations in the human body (gastrointestinal system, urogenital system, blood vessels, skin), its tumours are of diverse locations as well. Most frequently smooth muscle tumours develop in the gastrointestinal and in the urogenital system. They occur in the skin less frequently, while their development in the deeper soft tissue is ever rarer. The following sometimes bizarre, but rare phenomena seem to contradict benignity.
II./2.4.1.: Intravascular leiomyomatosis
In periuterine varices and in the inferior vena cava benign morphology is sometimes accompanied by multiple, intraluminar smooth muscle tumours (so-called intravascular leiomyomatosis). Without being malignant, they can cause severe circulatory obstructions because of their intravascular growth. During surgeries when their connection with the vascular wall is detached at the place of their development, they can be pulled out of the vessel like a snake. Sometimes they are accompanied by thrombosis, from which embolisations can develop.
II./2.4.2.: Benignus metastizingleiomyoma
Besides the uterus, in other cases synchronous leiomyomata can develop in the lung as well. The name is obviously misleading, since the tumour is not a metastasis of the uterine tumour, but more likely the result of a parallel tumour development.
II./2.4.3.: Disseminated peritoneal leiomyomatosis
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Along the uterine corporal tumours rarely small leiomyomata can occur sporadically on the peritoneum and on the omentum, giving the impression of a metastatic malignant process. However, the tumours in these cases are independently developing extrauterine tumours, which occur simultaneously in the uterus and in the above mentioned locations. Accordingly, their biological behaviour is benign as well.
II./2.4.4.: Oesophageal leiomyoma
Oesophageal leiomyomata are the most frequent benign tumours of the oesophagus. Their estimated occurrance rate, which is based on detailed pathological examinations, is almost 8%. Almost half of the clinically detected and surgically removed cases are asymptomatic tumours of accidental findings. In the other half main symptoms include disturbed swallowing (dysphagia) and uncertain chest pain. Most leiomyomata of oesophageal origin develop in the inner, circular layer of the muscular wall, mainly in the lower third of the oesophagus.
Sometimes more tumours grow simultaneously. In these cases the possibility of a synchronous development of pulmonary and uterine leiomyomata has to be considered. The possibility that these multiplex, multiorgan tumours are part of type-1 multiplex endocrin neoplasia (MEN-1) syndrome has to be also considered. Their macro- and microscopic appearance is identical to uterine leoimyomata. If they protrude into the lumen they lift the covering mucous membrane and form the picture of a broad-based (sessile) or less frequently of a peduncular polyp. Ulceration of the mucous membrane is a rare complication. If it occurs, then it usually develops close to the pit of the stomach (cardia) and is accompanied with reflux. It is usually treated with local resection or enucleation.
II./2.4.5.: Gastric leiomyoma
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Gastric leiomyoma is a part of the wide group of gastrointestinal mesenchymal tumours as a distinct subgroup of smooth muscle origin. This is underlined by the immunohistological observation that the tumour cells give positive reactions for antibodies against smooth muscle actin (SMA), desmin, calponin, caldesmon, myosin, and ultrastructurally myofilaments are present in the cytoplasm. The tumours can derive from the layers of the tunica muscularis propria, of the lamina muscularis mucosae or from the wall of the mural vessels. In its differential diagnosis gastrointestinal stromal tumour (GIST) has to be mentioned primarily.
II./2.4.6.: Leiomyoma of the colon
Smooth muscle tumours of the colon are mainly located in the rectum, where they appear in the form of small and benign nodes. The upper fractions of the colon are more likely to become malignant. Like usually in the gastrointestinal tract, the size of the tumour is a relatively good indicator of the risk of malignancy. Sometimes the tumours are multifocal. In these cases they can be accompanied by similar, multiple tumours of the small intestine.
II./2.4.7.: Leiomyomata of the skin
Leiomyomata of the skin can be divided into two groups. Cutaneous leiomyoma (i) is more frequent. The tumour develops from the arrector pili muscule surrounding the follicles. It can also occur in the genital areas. The nodules are often multiplex, painful, but harmless. Histologically the tumour consists of mature smooth muscle fibres, which are easy to recognize. The other group occurring in the skin is the (ii) cutaneous angiomyoma (vascular leiomyoma, which is more frequent in women. The lesion is painful and can be found deeper in the skin, in the subcutaneous tissue. Histologically the leiomyoma consists of smooth muscle fibres with diverse courses located among vessels with thick walls.
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