Hematological diseases can be either primary, i.e. caused by disorders in blood-forming organs themselves, or secondary, reflecting the involvement of any other systems. Examination of blood cell morphology (cytological, histological, histochemical, immunohistochemical, etc., tests) is performed either on a smear or on puncture material from the bone marrow or lymph nodes. Aspiration biopsy and trepanobiopsy specimens (trepanobiopsy is bone puncture with a special needle, usually in the iliac crest area).
Hematopoiesis is a process of cellular differentiation resulting in mature blood cell formation.