A vascular tumor is a tumor of vascular origin; a soft tissue growth that can be either benign or malignant, formed from blood vessels or lymph vessels. Examples of vascular tumors include hemangiomas, lymphangiomas, hemangioendotheliomas, Kaposis sarcomas, angiosarcomas, and hemangioblastomas. An angioma refers to any type of benign vascular tumor.Some vascular tumors can be associated with serious blood-clotting disorders, making correct diagnosis critical.A vascular tumor may be described in terms of being highly vascularized, or poorly vascularized, referring to the degree of blood supply to the tumor. Classification
Vascular tumors make up one of the classifications of vascular anomalies. The other grouping is vascular malformations. Vascular tumors can be further subclassified as being benign, borderline or aggressive, and malignant. Vascular tumors are described as proliferative, and vascular malformations as nonproliferative. Types
A vascular tumor typically grows quickly by the proliferation of endothelial cells. Most are not birth defects. Benign
The most common type of benign vascular tumors are hemangiomas, most commonly infantile hemangiomas, and less commonly congenital hemangiomas. Infantile hemangioma
Infantile hemangiomas are the most common type of vascular tumor to affect babies, accounting for 90% of hemangiomas. They are characterised by the abnormal proliferation of endothelial cells and of deviant blood vessel formation or architecture. Hypoxic stress seems to be a major trigger for this. Infantile hemangiomas are easily diagnosed, and little if any aggressive treatment is needed. They are characterised by rapid growth in the first few months, followed by spontaneous regression in early childhood.
The FDAs Gastrointestinal Drugs Advisory Committee referred to the drugs efficacy as "modest", highlighting that the placebo brought relief on the primary outcome measure to 40–50% of women. Contraindications
Lotronexs prescribing information brochure states that alosetron should not be initiated in patients with constipation. Other contraindications are: history of chronic or severe constipation or sequelae from constipation; intestinal obstruction, stricture, toxic megacolon, gastrointestinal perforation, and/or adhesions, ischemic colitis, impaired intestinal circulation, thrombophlebitis, or hypercoagulable state; Crohns disease or ulcerative colitis; diverticulitis; severe hepatic impairment. Concomitant use of fluvoxamine is also contraindicated. Adverse effects
Alosetron was withdrawn in 2000 following the association of alosetron with serious life-threatening gastrointestinal adverse effects. The cumulative incidence of ischaemic colitis was 2 in 1000, while serious complications arising from constipation (obstruction, perforation, impaction, toxic megacolon, secondary colonic ischaemia, death) was 1 in 1000. A 1999 review performed by FDA medical officer John Senior, indicated that 27% of patients experienced constipation. The phase III trial reported constipation occurred in 30% and 3% of patients in the alosetron and placebo groups, respectively. It was cited as the most important reason for patients dropping out of the study. Mechanism of action
Alosetron has an antagonist action on the 5-HT3 receptors of the enteric nervous system of the gastrointestinal tract. While being a 5-HT3 antagonist like ondansetron, it is not classified or approved as an antiemetic.