The term "giant platelet" is usually used when the platelets are as large as or larger than the red blood cells (RBCs) in the microscopic field, if the MCV is normal. The cell shape may be round and smooth or scalloped and irregular.
Giant platelets may be seen in myeloproliferative and myelodysplastic conditions, autoimmune thrombocytopenia, in association with severe leukemoid reactions, and in inherited conditions such as May-Hegglin anomaly and Bernard-Soulier syndrome. Their presence in the peripheral blood smear should lead to further investigation for their meaning. The image on the right is a giant platelet that is observed in a case of May-Hegglin anomaly.
