This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
Bone marrow finding in myelofibrosis- 
Select and explain. 
A. Dry tap (hypocellular), B. Megaloblastic cells, C. Microcytic cells, D. Thrombocytosis
A: Dry tap (hypocellular)
Answer: A: Dry tap (hypocellular) 
Explanation: Dry tap is usually defined as a "failure to obtain bone marrow on attempted marrow aspiration". The diagnosis and management of many haematological diseases depends on examination of the bone marrow, which involves two separate specimens i.e. a cytologic and a histologic preparation.Bone marrow examination refers to the pathologic analysis of samples of bone marrow obtained by bone marrow biopsy (often called a trephine biopsy) and bone marrow aspiration. Bone marrow examination is used in the diagnosis of a number of conditions, including leukemia, multiple myeloma, lymphoma, anemia, and pancytopenia. The bone marrow produces the cellular elements of the blood, including platelets, red blood cells and white blood cells. While much information can be gleaned by testing the blood itself (drawn from a vein by phlebotomy), it is sometimes necessary to examine the source of the blood cells in the bone marrow to obtain more information on hematopoiesis; this is the role of bone marrow aspiration and biopsy.