Does morphology matter in 2017? An approach to morphologic clues in non-neoplastic blood and bone marrow disorders

Numerous non-neoplastic and neoplastic conditions manifest with distinctive features in blood. Although automated complete blood count (CBC) data are essential, CBC information alone is insufficient for diagnosis. Consequently, morphologic review of blood smears is still relevant in the era of sophisticated automated analyzer systems. Pathologist interpretation of the peripheral blood smear, in conjunction with CBC and clinical information, can provide rapid diagnostic information and guide cost-effective targeted laboratory testing. Pathologist review of blood smears can be used to diagnose cases in which the clinical findings are misleading or nonspecific. Here, we discuss a selection of cases in which the pathologist examination of the blood smear can aid in rapid and accurate diagnosis and guide appropriate treatment. Exemplary non-neoplastic disorders with distinctive morphologic blood features of RBC, neutrophils, monocytes, and lymphocytes will be highlighted. The differential diagnostic considerations in blood smears with RBC destruction will be presented, expanding beyond microangiopathic hemolytic anemia. Lymphocyte morphologic assessment guides differential diagnosis including the identification of rare germline disorders. In each case presented, the integration of morphologic features guided additional testing with confirmation of the diagnosis. Peripheral blood smear review is timely and cost effective, even in an era of sophisticated automated laboratory testing.