WBR0781

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Hematology, SubCategory::Oncology
Prompt	[[Prompt::A 32-year-old man presents to his primary care physician with 1 month of weakness and fatigue. The patient reports that he has also been short of breath with minor activity. On physical exam, the physician notices several bruises on the patient’s abdomen and lower extremities although the patient denies any trauma. Splenomegaly is also noted 5 cm below the left costal margin. The physician orders a set of labs and a blood smear that are shown below. What other findings do you expect to observe? Hemoglobin = 6.8 MCV = 78 White Blood Cells = 17230 %Neutrophils = 4% %Lymphocytes = 96% Platelets = 13000 ]]
Answer A	AnswerA::Terminal deoxynucleotidyl transferase positivity on immunohistochemistry
Answer A Explanation	AnswerAExp::Terminal deoxynucleotidyl transferase (TdT) is a DNA polymerase expressed in immature B and T cells and is used in the diagnosis of acute lymphoblastic leukemia specifically pre-B and pre-T subtypes.
Answer B	AnswerB::Peroxidase positivity
Answer B Explanation	AnswerBExp::Peroxidase positivity is seen in AML cells due to the presence of Auer rods.
Answer C	AnswerC::Schistocytes
Answer C Explanation	AnswerCExp::Schistocytes are seen in patients with microangiopathic hemolytic anemia like TTP or DIC.
Answer D	AnswerD::Bite cells and Heinz bodies
Answer D Explanation	AnswerDExp::Both bite cells and heinz cells are seen in patients with hemolytic anemia secondary to G6PD deficiency.
Answer E	AnswerE::Tartrate-resistant acid phosphatase stain positivity
Answer E Explanation	AnswerEExp::Tartrate-resistant acid phosphatase (TRAP) positivity is typical of hairy cell leukemia.
Right Answer	RightAnswer::E
Explanation	[[Explanation::Hairy cell leukemia is a slowly progressive hematologic malignancy classically seen in older males. Patients usually present with anemia, thrombocytopenia and neutropenia despite normal or elevated white cell count. On physical exam, splenomegaly is common with easy bruising secondary to low platelets. Diagnosis is usually made by peripheral blood as well as bone marrow smear showing characteristic hairy cells (white blood cells with irregular, hair-like margins). The origin of hairy cells is B-lymphocytes although they may exhibit features of monocytes. The diagnosis can be confirmed by staining with tartrate-resistant acid phosphatase (TRAP). TRAP is a glycosylated enzyme expressed normally in other tissues (osteoclasts) but is markedly increased in "hairy cells". Patients are usually at very high risk of infection given their immune status. Educational Objective: Hairy cell leukemia presents with cytopenia and splenomegaly with peripheral and bone marrow smear showing hairy cells. Tartrate-resistant acid phosphatase (TRAP) positivity may be used to confirm the diagnosis. References: Zinzani PL, Pellegrini C, Stefoni V, et al. Hairy cell leukemia: evaluation of the long-term outcome in 121 patients. Cancer. 2010;116(20):4788-92.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Hairy cell leukemia, WBRKeyword::TRAP, WBRKeyword::Leukemia
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::