Rapid review: haematology and oncology

• This page revises the haematology-oncology emergencies and classic presentations a medical student must recognise fast. It is a revision page, not a substitute for the full MedGrasp topics it names.
• Sort anaemia by mean cell volume (MCV) first: microcytic (under 82 fL), normocytic (82 to 98 fL), macrocytic (over 98 fL), then ask haemolysis or blood loss versus marrow failure with the reticulocyte count. ^[1]
• A bleeding patient needs a platelet count and a clotting screen before labels; splenomegaly or failure to respond to treatment points to bone marrow disease, not simple immune thrombocytopenia.
• Cancer emergencies are time-critical: neutropenic fever, tumour lysis, cord compression, superior vena cava obstruction and hypercalcaemia must each be treated on suspicion, before the scan report returns.
• In metastatic spinal cord compression the level of neurological function on arrival predicts outcome; dexamethasone 16 mg and immobilisation come before the MRI.
• Common cancers are confirmed by biopsy and staged by imaging; first-line treatment follows the tissue diagnosis, never the blood test alone.
• When two sources give different numbers, the difference is real: check the guideline year in brackets and follow your local protocol.

By the end of this page you should be able to:

1. Give the most likely diagnosis, best first test and best first treatment for each classic haematology-oncology presentation listed below.
2. Name the commonest wrong answer for each presentation and say why it is wrong.
3. Apply an approach algorithm to anaemia, bleeding, thrombosis and a sick cancer patient.
4. Recognise five oncologic emergencies and the first 24 hours of management.
5. Link each block to its full MedGrasp topic by its discipline and slug (written out in full as plain text).

Start with the presenting picture in plain clinical words, then read the single most likely diagnosis, then the best first test, then the best first treatment, then the commonest wrong answer. The wrong answer is often the diagnosis you reach if you stop thinking too early. Each block names the full MedGrasp topic by plain text so that you can open it; examples are the full topics "hematology-oncology/anaemia-approach-and-iron-deficiency" and "hematology-oncology/oncologic-emergencies". Figures and full dosing live on those pages.

Classification by MCV is the first step. A normal MCV is 82 to 98 fL; under 82 fL is microcytic and over 98 fL is macrocytic. ^[1] Anaemia is a symptom of an underlying condition and is defined by haemoglobin below WHO 2024 cut-offs, which vary by age, sex, pregnancy, smoking and altitude. ^[2] Iron deficiency is a common and treatable cause of microcytic anaemia, so it is a sensible first thought in microcytic disease, although thalassaemia trait, chronic disease and sideroblastic anaemia must be excluded. Then use the reticulocyte count: if the marrow can respond the anaemia is regenerative (bleeding or haemolysis), if it cannot the anaemia is hypo-regenerative (deficiency, chronic disease, renal failure or marrow disease). ^[1]

Full topics: "hematology-oncology/anaemia-approach-and-iron-deficiency", "hematology-oncology/sideroblastic-and-megaloblastic-anaemia", "hematology-oncology/thalassaemias", "hematology-oncology/haemolytic-anaemias", "hematology-oncology/sickle-cell-disease", "hematology-oncology/aplastic-anaemia", and "hematology-oncology/polycythaemia-and-myeloproliferative-neoplasms".

Presentations:

• Microcytic anaemia with low ferritin and high total iron-binding capacity. Most likely diagnosis: iron deficiency anaemia. Best first test: full blood count, film and ferritin (transferrin saturation if inflamed). Best first treatment: find the source of blood loss; oral or intravenous iron replacement while investigating. Commonest wrong answer: "it must be diet alone" in an adult man or postmenopausal woman; look for gastrointestinal blood loss. ^{[1] [2]}
• Microcytic anaemia with normal iron studies. Most likely diagnosis: thalassaemia trait. Best first test: haemoglobin electrophoresis or genetic testing, with a normal red cell distribution width. Best first treatment: counselling and family screening, not iron. Commonest wrong answer: prescribing iron to a patient with a normal ferritin, which delays the correct diagnosis. ^[1]
• Macrocytic anaemia with a low vitamin B12. Most likely diagnosis: vitamin B12 deficiency, pernicious anaemia if autoantibodies are present. Best first test: B12, folate and intrinsic factor antibodies, with careful neurological examination. Best first treatment: B12 replacement (parenteral if malabsorption or neurological signs). Commonest wrong answer: giving folate alone, which corrects the blood count but allows neurological damage to progress. Full topic: "hematology-oncology/sideroblastic-and-megaloblastic-anaemia".
• Pancytopenia with a hypocellular marrow. Most likely diagnosis: aplastic anaemia. Best first test: full blood count and bone marrow biopsy. Best first treatment: specialist haematology; supportive care, then immunosuppression or transplantation by severity and age. Commonest wrong answer: treating it as simple iron deficiency because of anaemia alone. Full topic: "hematology-oncology/aplastic-anaemia".
• Normocytic anaemia in chronic disease. Most likely diagnosis: anaemia of chronic disease, often with functional iron deficiency. Best first test: ferritin and C-reactive protein together (ferritin rises in inflammation), plus kidney function. Best first treatment: treat the underlying disease; iron helps only if iron deficiency coexists. Commonest wrong answer: giving iron when ferritin is already high. ^[1]

• Symptomatic anaemia at any haemoglobin, or rapidly falling haemoglobin; the decision to transfuse is clinical.
• Unexplained microcytic anaemia in a young woman may still need coeliac screening; in older adults it needs gastrointestinal investigation. ^[1]
• A reticulocyte count over 3 with falling haemoglobin points to haemolysis or bleeding, not marrow failure. ^[1]
• A normal MCV that is rising during treatment for iron deficiency suggests mixed deficiency, classic in coeliac disease or autoimmune gastritis.

Presentations:

• Petechiae, bruising and a low platelet count. Most likely diagnosis: immune thrombocytopenia in a well patient. Best first test: full blood count and blood film (often enough), with marrow only if red flags. Best first treatment: observe if mild, or steroids or intravenous immunoglobulin as guided by bleeding. Commonest wrong answer: calling any low platelet count an emergency; context and platelet level separate watchful waiting from treatment. Full topic: "hematology-oncology/immune-thrombocytopenia".
• A child with pallor, petechiae, fever and hepatosplenomegaly. Most likely diagnosis: acute leukaemia. Best first test: full blood count, film and bone marrow examination. Best first treatment: urgent referral, hydration and infection control before chemotherapy. Commonest wrong answer: watchful waiting for "a likely viral illness"; a blood count changes that plan.
• Easy bruising with a prolonged activated partial thromboplastin time that corrects on mixing. Most likely diagnosis: factor deficiency, most often haemophilia or von Willebrand disease. Best first test: factor assays after mixing studies. Best first treatment: replace the missing factor with desmopressin or factor concentrate as type and severity dictate. Commonest wrong answer: dismissing mild mucocutaneous bleeding; von Willebrand disease is common and often underdiagnosed. Full topics: "hematology-oncology/haemophilia" and "hematology-oncology/von-willebrand-disease".
• Thrombocytopenia with neurological or renal features after heparin. Most likely diagnosis: heparin-induced thrombocytopenia. Best first test: clinical 4T score, then PF4 antibody and functional testing. Best first treatment: stop heparin immediately and start a non-heparin anticoagulant. Commonest wrong answer: continuing or reintroducing heparin because the platelet count is only moderately low. Full topic: "hematology-oncology/hypercoagulable-states-and-hit".
• Sepsis with oozing from lines and a consumptive picture. Most likely diagnosis: disseminated intravascular coagulation. Best first test: platelet count, prothrombin time, activated partial thromboplastin time, fibrinogen and D-dimer with ISTH criteria. Best first treatment: treat the trigger; replace consumed factors and platelets for bleeding. Commonest wrong answer: anticoagulating a bleeding patient first; haemorrhage dominates in most acute presentations. Full topic: "hematology-oncology/disseminated-intravascular-coagulation".

Presentations:

• Unilateral swollen, tender leg after surgery or immobilisation. Most likely diagnosis: deep vein thrombosis. Best first test: compression ultrasound of the proximal leg veins. Best first treatment: anticoagulation (direct oral anticoagulant or heparin then transition) unless contraindicated, plus leg elevation and early mobilisation where allowed. Commonest wrong answer: waiting for D-dimer in a patient with high pre-test probability; imaging is the safer first step.
• Sudden pleuritic chest pain, dyspnoea and tachycardia. Most likely diagnosis: pulmonary embolism. Best first test: CT pulmonary angiography in unstable or high-probability patients; ventilation-perfusion scanning or D-dimer-guided pathways in stable, low-probability patients. Best first treatment: immediate anticoagulation; thrombolysis or embolectomy for shock. Commonest wrong answer: treating as isolated pneumonia without excluding a clot, or giving thrombolysis without evidence of shock.
• Clot despite anticoagulation, or a first clot in a young patient with family history. Most likely diagnosis: thrombophilia (inherited or acquired). Best first test: targeted thrombophilia testing rather than a blanket screen, guided by the event and its context. Best first treatment: treat the acute clot first; test later if it changes long-term management. Commonest wrong answer: testing everyone immediately and changing anticoagulation on a single result. Full topic: "hematology-oncology/hypercoagulable-states-and-hit".
• VTE in active cancer. Most likely diagnosis: cancer-associated thrombosis. Best first test: compression ultrasound or CT pulmonary angiography, plus renal function and bleeding risk assessment. Best first treatment: a low-molecular-weight heparin or a directly acting oral anticoagulant chosen by bleeding risk and cancer type. Commonest wrong answer: stopping anticoagulation because the cancer is being treated; clots recur while cancer is active. Full topic: "hematology-oncology/vte-in-cancer-and-prophylaxis".

Presentations:

• Pancytopenia with circulating blasts in a child or young adult. Most likely diagnosis: acute lymphoblastic leukaemia. Best first test: full blood count, film, immunophenotyping and bone marrow aspirate. Best first treatment: urgent referral for induction chemotherapy and infection prophylaxis. Commonest wrong answer: treating the anaemia with transfusion alone and delaying the diagnosis.
• Auer rods and a high white cell count in an adult. Most likely diagnosis: acute myeloid leukaemia. Best first test: full blood count, film, flow cytometry and cytogenetics (watch for promyelocytic (APL) disease). Best first treatment: if acute promyelocytic leukaemia is suspected, start all-trans retinoic acid (45 mg per m2 daily) and arrange arsenic trioxide, while correcting coagulopathy before any procedure. Commonest wrong answer: performing a lumbar puncture or central line before reversing the disseminated coagulopathy of acute promyelocytic leukaemia. ^[3]
• Marked lymphocytosis in older adults. Most likely diagnosis: chronic lymphocytic leukaemia. Best first test: full blood count, immunophenotyping and fluorescence in situ hybridisation. Best first treatment: often watchful waiting; start targeted therapy for progressive disease, recurrent infection or cytopenia. Commonest wrong answer: treating the diagnosis the day it is made rather than the disease.
• Leukocytosis with a low neutrophil alkaline phosphatase and a translocation. Most likely diagnosis: chronic myeloid leukaemia. Best first test: karyotype and BCR-ABL1 testing. Best first treatment: a tyrosine kinase inhibitor. Commonest wrong answer: giving busulfan-style cytoreduction without knowing the phase of disease.
• Painless rubbery cervical lymphadenopathy in a young adult. Most likely diagnosis: Hodgkin lymphoma. Best first test: excision biopsy for histology and PET-CT staging. Best first treatment: staged combination chemotherapy (often ABVD) with or without radiotherapy by PET response. Commonest wrong answer: fine-needle aspiration alone, which does not provide the architecture needed for diagnosis. ^[4]
• Rapidly growing nodal mass with night sweats and weight loss. Most likely diagnosis: aggressive non-Hodgkin lymphoma, such as diffuse large B-cell lymphoma. Best first test: excision biopsy, PET-CT and lactate dehydrogenase. Best first treatment: R-CHOP-like chemoimmunotherapy. Commonest wrong answer: treating a clinical guess without tissue, because the therapy differs by subtype.
• Splenomegaly with "fried egg" cells and pancytopenia. Most likely diagnosis: hairy cell leukaemia. Best first test: blood film and tartrate-resistant acid phosphatase stain or immunophenotyping. Best first treatment: a purine analogue. Commonest wrong answer: confusing it with chronic lymphocytic leukaemia and watching it.

Full topics: "hematology-oncology/acute-leukaemias", "hematology-oncology/chronic-lymphocytic-leukaemia", "hematology-oncology/cml-and-hairy-cell-leukaemia", "hematology-oncology/hodgkin-lymphoma", and "hematology-oncology/non-hodgkin-lymphoma".

Presentations:

• Bone pain, anaemia, renal impairment and hypercalcaemia in an older adult. Most likely diagnosis: multiple myeloma. Best first test: serum protein electrophoresis, serum free light chains and skeletal imaging, then marrow examination. Best first treatment: hydration, correction of hypercalcaemia and analgesia, then systemic therapy chosen by fitness. Commonest wrong answer: treating the bone pain as simple osteoarthritis and missing the paraprotein. ^[10]
• Hyperviscosity with bleeding and visual disturbance. Most likely diagnosis: Waldenstrom macroglobulinaemia. Best first test: serum IgM level and viscosity, with marrow examination. Best first treatment: plasmapheresis for severe symptoms, then systemic therapy. Commonest wrong answer: anticoagulating without addressing the IgM burden.
• A solitary lytic bone lesion with plasmacytoid cells. Most likely diagnosis: solitary plasmacytoma or early myeloma. Best first test: full myeloma panel and whole-body imaging. Best first treatment: local radiotherapy with systemic staging to decide whether therapy beyond the lesion is needed. Commonest wrong answer: declaring it multiple myeloma without marrow and myeloma-defining features.

Presentation: a chemotherapy patient with temperature 38 C or higher and neutrophils 0.5 x 10^9 per L or lower. Most likely diagnosis: neutropenic sepsis. Best first test: blood cultures before antibiotics if they do not delay treatment; full blood count, renal function, lactate and C-reactive protein. Best first treatment: empiric broad-spectrum intravenous antibiotics immediately; NICE CG151 (2012, last reviewed 2020) advises beta-lactam monotherapy, and piperacillin with tazobactam is a standard choice, with escalation if there is microbiological or clinical reason. ^[6] The MASCC score stratifies risk: 21 or higher marks low risk and points to outpatient or ambulatory management; under 21 is high risk. ^[7] Prophylactic fluoroquinolone is offered to adults with anticipated significant neutropenia from chemotherapy, and G-CSF is not routinely used for prevention unless it is part of the regimen or needed to maintain dose intensity. ^[6] A neutrophil count of 0.5 x 10^9 per L or lower defines significant neutropenia. ^[6] Commonest wrong answer: waiting for cultures or imaging before giving antibiotics; delay is the killer. Commonest trap: adding glycopeptides or aminoglycosides routinely, which NICE advises against without a microbiological indication. ^[6]

Full topic: "hematology-oncology/neutropenia" and "hematology-oncology/neutropenic-fever".

Presentation: a high-grade lymphoma or leukaemia patient in the first days of treatment, with rising creatinine, potassium, phosphate and urate. Most likely diagnosis: tumour lysis syndrome. Best first test: urea, creatinine, potassium, phosphate, calcium and urate. Best first treatment: aggressive intravenous fluids, correct potassium (calcium gluconate for ECG change, insulin and glucose to shift it), and rasburicase for high-risk or established disease; allopurinol as the alternative where rasburicase is unavailable or contraindicated (a typical adult dose is often quoted in local protocols). Do not correct asymptomatic hypocalcaemia. Doses and thresholds: rasburicase 0.15 to 0.20 mg per kilogram daily, capped at 6 mg; Cairo-Bishop (Labonté's review, 2026) biochemical thresholds are uric acid at least 476 micromol per L, potassium at least 6 mmol per L, phosphate at least 1.45 mmol per L in adults (at least 2.1 mmol per L in children), and calcium no more than 1.75 mmol per L, with a 25 percent change from baseline also qualifying. Clinical tumour lysis needs acute kidney injury, arrhythmia, seizure or death as well. ^[8] Commonest wrong answer: alkalinising urine routinely, which promotes calcium-phosphate precipitation. Commonest trap: forgetting to screen at-risk patients for glucose-6-phosphate dehydrogenase deficiency before rasburicase. ^[8]

Presentation: a cancer patient, most often breast, lung, prostate or myeloma, with back pain then weakness, numbness or sphincter change. Most likely diagnosis: metastatic spinal cord compression. Best first test: urgent whole-spine MRI, to be done within 24 hours when suspected. Best first treatment: immobilise if unstable, give oral dexamethasone 16 mg (or equivalent parenteral dose) immediately and then 16 mg daily while awaiting surgery or radiotherapy, then urgent radiotherapy (commonly 8 Gy in one fraction) or surgical decompression for instability or neurological deterioration. ^[9] Commonest wrong answer: arranging a plain X-ray and waiting for the result; it cannot exclude the diagnosis. Commonest trap: forgetting that neurological function at presentation is the strongest predictor of outcome, so treat on suspicion. ^[9]

Presentation: facial and arm swelling, dilated neck veins, dyspnoea and cough, progressing to confusion, stridor or hypotension. Most likely diagnosis: obstruction of the superior vena cava, malignant in the great majority, from lung cancer or lymphoma. Best first test: contrast-enhanced CT of the chest. Best first treatment: temporising oxygen, elevation of the head and cautious diuretics or steroids, then endovascular stenting for severe disease and radiotherapy or chemotherapy for the underlying tumour. Commonest wrong answer: radiotherapy first in a patient who is peri-arrest; stenting gives the fastest relief. Grade 4 disease needs airway protection and urgent decompression.

Presentation: fatigue, confusion, polyuria, constipation and dehydration in breast, lung or renal cancer or myeloma. Most likely diagnosis: hypercalcaemia of malignancy, usually from PTHrP or bone metastases. Best first test: corrected calcium, phosphate, urea and creatinine, albumin, ECG, with PTH and PTHrP if the cause is unclear. Best first treatment: 0.9 percent saline 200 to 500 mL per hour first, then an antiresorptive; severe disease gets salmon calcitonin as a bridge. Endocrine Society guidance suggests denosumab first-line; in practice many services use zoledronic acid 4 mg intravenously (3 mg if creatinine clearance is 30 to 60 mL per minute, avoid if under 30), and guidelines differ on this choice. ^[5] Severity: mild calcium under 3.0 mmol per L, moderate 3.0 to 3.5, severe over 3.5. ^[5] Commonest wrong answer: loop diuretics before adequate rehydration, which worsens renal failure. For calcitriol-mediated disease (usually lymphoma) use high-dose glucocorticoids first. ^[5]

Common cancers are diagnosed by tissue, not by a single test: a clinical suspicion plus imaging identifies the lesion, and biopsy confirms it. Staging then uses the TNM system and performance status. ^[11] Typical first steps:

Full topic for staging, screening and markers: "hematology-oncology/cancer-staging-screening-and-tumour-markers".

• Fever 38 C or higher during chemotherapy with a low or unknown neutrophil count: treat as an emergency.
• A cancer patient with new back pain, paraesthesia, leg weakness or sphincter disturbance: spinal cord compression until proven otherwise.
• Facial or arm swelling with dyspnoea, confusion or stridor: superior vena cava obstruction.
• Confusion or excessive thirst with a high corrected calcium.
• A rising creatinine and potassium after starting treatment for leukaemia or lymphoma.
• Dehydration, oliguria or arrhythmia in a patient at risk of tumour lysis.

• Older adults tolerate large fluid challenges poorly, so watch for pulmonary oedema behind aggressive hydration.
• In pregnancy, radiotherapy and chemotherapy decisions, and steroid use, must be made with the obstetric and oncology teams.
• Children develop tumour lysis more often and more severely after induction for acute lymphoblastic leukaemia and Burkitt lymphoma, so risk-stratify before the first dose.
• Immunocompromised patients can be septic with low-grade or absent fever.

• Time to antibiotics matters more than which antibiotic in neutropenic fever; blood cultures, a thermometer and a first dose of a broad-spectrum beta-lactam are achievable in most settings.
• Tumour lysis responds to fluids, allopurinol and careful electrolyte monitoring; dialysis may require early transfer.
• Spinal cord compression may be diagnosed clinically and treated with immobilisation and dexamethasone while arranging transfer.
• Superior vena cava obstruction without stenting relies on radiotherapy, chemotherapy and temporising measures.
• Hypercalcaemia: saline, calcitonin and carefully used loop diuretics are widely available; zoledronic acid is cheap in many settings.

hematology-oncology/anaemia-approach-and-iron-deficiency; hematology-oncology/sideroblastic-and-megaloblastic-anaemia; hematology-oncology/thalassaemias; hematology-oncology/haemolytic-anaemias; hematology-oncology/sickle-cell-disease; hematology-oncology/aplastic-anaemia; hematology-oncology/polycythaemia-and-myeloproliferative-neoplasms; hematology-oncology/normal-haemostasis; hematology-oncology/haemophilia; hematology-oncology/von-willebrand-disease; hematology-oncology/immune-thrombocytopenia; hematology-oncology/hypercoagulable-states-and-hit; hematology-oncology/vte-in-cancer-and-prophylaxis; hematology-oncology/disseminated-intravascular-coagulation; hematology-oncology/acute-leukaemias; hematology-oncology/chronic-lymphocytic-leukaemia; hematology-oncology/cml-and-hairy-cell-leukaemia; hematology-oncology/hodgkin-lymphoma; hematology-oncology/non-hodgkin-lymphoma; hematology-oncology/multiple-myeloma; hematology-oncology/waldenstrom-and-amyloidosis; hematology-oncology/neutropenia; hematology-oncology/neutropenic-fever; hematology-oncology/oncologic-emergencies; hematology-oncology/cancer-staging-screening-and-tumour-markers.