Leukemoid Reaction (LR)

Patient will have a severe infection that may require longer than normal to improve even with antibiotics. On CBC, the WBC count will be markedly elevated (typically >50,000). On peripheral smear, there will be many immature forms of neutrophils (myelocytes, promyelocytes, metamyelocytes, bands). However, most will be further along in maturation (i.e. more bands). Look for a high leukocyte alkaline phosphatase (LAP) score.

Differential Dx
The LAP score helps differentiate this from CML which can also present with infections as well as immature forms of neutrophils (myelocytes, metamyelocytes) but has a low LAP score. This is because the neutrophil precursors are so immature that they don't function as well. CML also usually has a higher WBC count (typically >100,000). Also unlike CML, leukemoid reaction does not present with increased basophils.

Relevant Images

More of the mature neutrophil precursors e.g. bands, metamyleocytes as well as mature (segmented) neutrophils.

Leukocyte alkaline phosphatase (LAP) score

High LAP score = leukemoid reaction

Low LAP score = CML

Comments

Chronic Myeloid Leukemia (CML)

Quick Review Patient is often older, and can no symptoms or have B symptoms (night sweats, etc), fatigue, and weight loss (caused by early satiety due to enlarged spleen). On physical exam, an enlarged spleen can be palpated. CBC shows very high WBC count (typically >100,000) with elevated basophils on differential. Peripheral smear shows early, immature neutrophil precursors (myelocytes, metamyelocytes) as well as many basophils. It is important for CML to know the details of the genetic abnormality because it relates to the treatment. CML is due to a translocation of BCR and ABL on chromosomes 9 and 22 resulting a fusion BCR-ABL gene that produces a tyrosine kinase that is always active. The treatment of choice is a tyrosine kinase inhibitor e.g. imatinib. They work to suppress the tyrosine kinase and can induce disease remission. Relevant Images Immature neutrophil precursors on peripheral smear BCR-ABL translocation

Chemotherapy

Terminology Adjuvant therapy - given in addition to standard therapy Consolidation therapy - given after induction therapy with multidrug regimens to further reduce tumor burden Induction therapy - initial dose of treatment to rapidly kill tumor cells and send the patient into remission Maintenance therapy - given after induction and consolidation therapies or after the initial standard therapy to kill any residual tumor cells and keep the patient in remission Neoadjuvant therapy - given before the standard therapy for a particular disease Remission - less than 5% tumor burden Salvage therapy - given when standard therapy fails Adjuvant therapies in various cancers Metastasis to bone - bisphosphonates (e.g. zoledronic acid) are given to prevent lytic lesions and pathologic fractures as well as malignant hypercalcemia. Bisphosphonates work by inhibiting osteoclasts and thereby preventing bone breakdown. Breast cancer Tamoxifen , a selective estrogen recep...

Acute Myeloid Leukemia (AML)

Quick Review Patient is an adult (usually older, but can also be younger) with fatigue (due to anemia) and bleeding (due to thrombocytopenia) and on CBC there is decreased hemoglobin, decreased platelets, and WBC varies (can be normal, increased or decreased). LDH will be elevated. The most important form of AML to know is acute promyelocytic leukemia (APML). On peripheral smear, AML presents with myeloblasts with Auer rods. Bone marrow biopsy will show myeloid blasts, for APML this would be atypical promyelocytes. In AML, the bone marrow is crowded with immature myeloid cells ("blasts") preventing development of other cell types (platelets, RBCs, normal WBCs). These myeloblasts are also present in the peripheral blood in large numbers. This is why patients have fatigue (anemia), bleeding/ bruising (thrombocytopenia), increased infections (granulocytopenia). APML can present with DIC (disseminated intravascular coagulation) which results in elevated PT and aPTT and re...

pathology

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