Unusual site thrombosis.

Venous thromboses in unusual sites are rare and heterogenous manifestations of venous thromboembolism (VTE). These uncommon diseases are each characterized by peculiar pathophysiological and clinical features, mainly reflecting the different characteristics of the organs of origin. Moreover, the relative frequency and importance of risk factors associated with their development may be different compared to those of the classical manifestations of VTE, such as deep vein thrombosis of the lower limbs or pulmonary embolism. The need for anticoagulant therapy for unusual site thrombosis (UST) is generally accepted. However, several questions remain unanswered: what is the best therapeutic agent, is it safe, and for how long should it be used? These questions persist mainly due to the low level of available evidence given the rarity of these diseases. The short- and long-term prognoses, and in particular the risk of recurrence and mortality, are quite heterogenous among the different manifestations of UST and even within each of them, depending mainly on the predisposing causes.