Blasts in pleural fluid: A clue to diagnose acute myeloid leukemia

Busara Songtanin MD, Abbie Evans BS, Irfan Warraich MD

Corresponding author: Busara Songtanin
Contact Information: Busara.Songtanin@ttuhsc.edu
DOI: 10.12746/swrccc.v10i43.1033


Acute myeloid leukemia is usually diagnosed in older patients, and its incidence increases with age. Most patients with acute myeloid leukemia present with symptoms related to anemia, bleeding, and infections. Blast infiltration into other tissues can occur. Leukemic pleural infiltration has been reported previously but is very rare. Here we discuss a 62-year-old woman diagnosed with acute myeloid leukemia with a leukemic infiltrate in a pleural effusion.

Keywords: AML, pleural effusion, blast cell, leukemic pleural infiltrate


Acute myeloid leukemia (AML) usually presents with constitutional symptoms. Pleural effusion is considered a rare manifestation of AML, and rapidly progressive pleural effusion together with leukemic pleural fluid infiltration is exceedingly rare in patients with AML. Here we discuss a patient with pleural effusion with leukemic blast cells as an initial presentation of AML.


A 62-year-old white woman with diabetes, hypothyroidism, asthma, and hypertension presented to our hospital with worsening cellulitis. Upon admission, she was noted to be hypoxemic and hypotensive with an oxygen saturation of 66% on room air; she required non-invasive ventilation and intravenous fluid for resuscitation. Respiratory examination revealed decreased breath sounds and dullness to percussion of the right lung base. Abdominal examination revealed splenomegaly. Chest x-ray showed multifocal opacities with bilateral small pleural effusions. The following day, the effusion increased significantly with total opacification of the right hemithorax. Thoracentesis was performed to improve her oxygenation. Serosanguinous fluid with numerous blasts were found in the pleural fluid consistent with leukemic exudative effusion (Figure). Pleural fluid analysis: red color, red blood cell 380,000/mm3, white blood cell 8,075/mm3, neutrophil 66%, lymphocyte 20%, monocyte 5%, lactate dehydrogenase 2,851 U/L, protein 2.5 gm/dL, glucose 151 mg/dL with serum protein 4.9 gm/dL and serum lactate hydrogenase 924 U/L.

Figure 1

Figure. Blasts with prominent nucleoli in pleural fluid (Thinprep Pap stain 200X).

Her complete blood counts showed a white blood count of 186.8/µL with 74.1% blasts, Hb 6.6 gm/dL, and platelet count 441/µL. Her baseline white blood count was 4.47/µL in 2020. Bone marrow aspiration showed 72% blasts. Flow cytometry revealed blasts that expressed CD13, CD33, CD34, CD45, CD 64, CD88, CD 117, and HLA-Dr. Computed tomography of the thorax revealed a right pleural effusion with loculations and reactive mediastinal lymphadenopathy. The patient initially required chest tube drainage for eight days.

She underwent leukapheresis that was complicated by tumor lysis syndrome. She then developed shock, which required vasopressors and multiple blood transfusions and atrial fibrillation that was controlled with diltiazem and amiodarone. She then required additional chest drainage for eight more days. Given her critical medical condition, she was given less intense chemotherapy using azacitidine and venetoclax. Repeat bone marrow biopsy showed morphologic and immunophenotypic findings consistent with persistent acute leukemia with 56% blast morphology. The patient was transferred to MD Anderson Cancer Center in Houston, Texas, for further management. She has not followed up in our hematology clinic.


Patients with AML usually present with constitutional symptoms such as fatigue or infection associated with pancytopenia. Although malignancy is the second leading cause of pleural effusion after infection, pleural effusion is uncommon in patients with AML, and fewer than 20 cases have been reported.1,2 In patients who developed malignant pleural effusions during their disease courses, approximately 1 in 5,000 had AML.1,3 In our report, a patient with no underlying hematological disorder presented to the hospital with respiratory symptoms and hypoxemia. Her chest x-ray showed a new pleural effusion. The differential diagnosis of pleural effusion includes infection, heart failure, malignancy, and collagen vascular disease. A complete blood count with markedly elevated leukocytes along with blast cells found on peripheral blood smear suggested an underlying malignancy in this patient. Thoracentesis revealed an exudative pleural effusion with blast cells.

Her pleural effusion represented leukemic infiltration into the pleural space; the underlying pathophysiology remains poorly understood, and the prognosis of disease in the presence of pleural effusion in AML is unknown. However, some reports suggest worse outcomes in these patients.4 The table summarizes representative cases in which the peripheral white blood cell count was reported. The white blood cell counts ranged from 6,500–86,000/µL, and the percent blasts ranged from 1% to 92%. The pleural effusion in our patient resolved after chest tube drainage and the initiation of chemotherapy. Treatment with hydroxyurea was previously used in an AML patient who initially presented with diffuse pulmonary infiltration and respiratory distress, and this drug decreased the blast cell count in the pleural fluid.5 Other chemotherapeutic regimens for ALM have led to resolution of leukemic pleural effusions.4 Patients with relapsing pleural effusions may require intrapleural chemotherapy or pleurodesis.6

Table. Summary of Representative Case Reports of AML in Pleural Effusions which Report Peripheral White Blood Cell Counts

Case Age Gender WBC (µL) Blasts (%) Treatment Response
Duhan6 26 Female 72,000 82 Cytarabine, daunorubicin, and cladribine Death
Chang7 74 Female 31,900 56.5 Cytarabine Complete remission
Chang7 74 Male 9,600 22 Supportive care Death
Raynold8 26 Male 6,500 1 Blood transfusions and oxytetracycline Death
Agrawal9 45 Male 86,000 92 Induction therapy (Exact medication not reported) Death 1 week later
Ou10 43 Male 11,500 Not reported Idarubicin, cytarabine Complete remission after cytarabine

In summary, leukemic infiltration of pleural fluid as a manifestation of acute myeloid leukemia is very unusual, and its pathogenesis is not fully understood. This case demonstrates the importance of pleural fluid analysis and cytologic studies to make a diagnosis in a patient who had no prior diagnosis of hematologic malignancy.

Consent: This patient gave consent for this publication.


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Article citation: Songtanin B, Evans A, Warraich I. Blasts in pleural fluid: A clue to diagnose acute myeloid leukemia. The Southwest Respiratory and Critical Care Chronicles 2022;10(43):26–28
From: Department of Internal Medicine (BS, AE) and Department of Pathology (IW), Texas Tech University Health Sciences Center, Lubbock, Texas
Submitted: 2/25/2022
Accepted: 2/27/2022
Conflicts of interest: none
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