Would cancer cause only elevated platelet count? my platelets are 420. i googled it and it was confusing so decided to ask here. no other symptoms. i do have low vitamin d and on iron supplements even though my iron been normal for over a year?

High platelet count can be the first and only sign of serious bone marrow disease, especially chronic myelogenous leukemia (CML), myelodysplasia, and similar problems. Early treatment is important and can be extremely helpful. If your platelet count remains in this range after 2-3 blood counts, ask your PCP for further evaluation, such as consultation with a hematologist-oncologist. Good luck.