Epidemiology

Etiology and pathogenesis

Rhabdomyosarcoma

Treatment

Arteriovenous Fistula

An arteriovenous fistula (AVF) is an abnormal connection or passageway between an artery and a vein. It may be: 1). congenital; 2). acquired due to pathologic process, such as trauma or erosion of an arterial aneurysm; 3). surgically created for hemodialysis treatments.

Congenital AVF, if small, usually do not need treatment. Acquired fistulas can be treated by surgery.

Rhabdomyosarcoma (RMS) is a malignant tumor of mesenchymal origin. RMS is a type of cancer, specifically a sarcoma (cancer of connective tissues), in which the cancer cells are thought to arise from skeletal muscle progenitors. It can also be found attached to muscle tissue, wrapped around intestines, or in any anatomic location. Most occur in areas naturally lacking in skeletal muscle, such as the head, neck, and genitourinary tract.

The two major histologic subtypes of RMS:

· embryonal (more common in younger children, the cancer cells resemble those of a typical 6-to-8-week embryo);

· alveolar (more common in older children and teenagers, they resemble those of a typical 10-to-12-week embryo).

Embryonal RMS (ERMS) is the most common type of RMS, affecting two thirds of all patients with disease.

ERMS occur more frequently in the head and neck region as compared with the extremities. Alveolar RMS (ARMS) occurs in older children, and tumors are most commonly located on the trunk or extremities.

Prognosis is worse in ARMS than ERMS, with a 5-year survival rate of 54%.

The exact nature of the pathogenesis of RMS is unclear; however, many hypotheses exist. It is largely thought that RMS arises as a consequence of regulatory disruption of skeletal muscle progenitor cell growth and differentiation. Pathogenic roles have been suggested for the MET proto-oncogene, which is involved in migration of myogenic precursor cells, and the TP53 proto-oncogene, which is responsible for tumor suppression.

Rhabdomyosarcoma is the most common type of soft tissue sarcoma diagnosed during the first 2 decades of life, accounting for 4,5% of all cases of childhood cancer. It is the third most common extracranial solid tumor of childhood after Wilms' tumor and neuroblastoma. Age at presentation follows a bimodal distribution, with peak incidences between 2 and 6 years and again between 10 and 18 years of age. This distribution reflects the incidences of the two major histologic subtypes of RMS. The incidence of embryonal RMS is highest at birth and extends through childhood before declining, while alveolar RMS peaks during childhood and adolescence. Approximately 65% of all RMS cases occur in children younger than 6 years of age. Slightly more males (58,4%) are affected than females (41,6%).

Дата добавления: 2014-10-15