In patients with thrombocytosis with negative MPN workup from peripheral blood and bone marrow, is there a role for daily 81mg aspirin or other treatment?

In the absence of an MPN, there is no data to support the use of low-dose ASA. Unless there was extreme thrombosis and acquired von Willebrand syndrome, there would also be little reason to bring the platelet count down as well. In the absence of MPN, thrombocytosis itself is not a risk factor for thrombosis.

Agree with Dr. @Dr. First Last. It would be unusual to have extreme thrombocytosis that is not related to an identifiable cause. If the bone marrow morphology is normal and extended NGS doesn't identify mutations, then every effort should be made to identify the cause of the thrombocytosis. As Dr. Gerds says, cytoreduction should not be initiated in patients without an MPN and aspirin, in this case, should only be given for other, non-MPN related issues, if indicated.