Giant platelets

These four images were taken from the 1997 Cytohematology Proficiency Test Event - Slide 005. All four images represent giant platelets. "Most normal sized platelets are 1.5 to 3 µm in diameter. Large platelets are 4 to 7 µm. Giant platelets are larger than 7 µm and usually 10 to 20 µm. For proficiency testing purposes, the term giant platelet is used when the platelet is larger than the size of the average red cell in the field, assuming a normal MCV." College of American Pathologists, Hematology Manual, 1998. Giant platelets may be seen in Bernard-Soulier syndrome and in myeloproliferative disorders (chronic myelogenous leukemia (CML), polycythemia vera, essential (primary) thrombocythemia, and agnogenic myeloid metaplasia).

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