ASH Image Bank (2001); doi:10.1182/ashimagebank-2001-100209
Copyright © 2001 by the American Society of Hematology.
Hairy Cell Leukemia
Peter Maslak, M.D.
Memorial Sloan-Kettering Cancer Center
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Figure 1. Hairy. Flow cytogram shows a white cell differential that is composed primarily of miscellaneous cells (large unclassified cells, or LUCs) and lymphocytes.
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Figure 2. Hairy. Hairy cell in the peripheral blood with characteristic cytoplasmic projections.(100X MacNeal Tetrachrome).
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Figure 3. Hairy. Clusters of hairy cells are visualized in the bone marrow aspirate (100X MacNeal Tetrachrome).
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Figure 4. Hairy. Hairy cell with an ovoid or kidney bean-shaped nucleus. Cytoplasmic projections are not as prominent as some of the other examples shown (100X MacNeal Tetrachrome).
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Figure 6. Hairy. Biopsy shows mononuclear cells with a characteristic clear zone surrounding the nucleus producing a fried egg appearance (40X H&E).
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Clinical Summary
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The patient is an 80-year-old man with a history of previously diagnosed hairy cell leukemia (HCL) who presents to evaluate increasing cytopenia. The patient was originally diagnosed with HCL approximately 15 years prior. He opted to undergo splenectomy at that time and received no chemotherapy. Following splenectomy, the patient had normalization of his blood counts.
The patient did well until 6 weeks prior to evaluation when he was found to have an abnormal complete blood cell count (CBC): white blood cell count (WBC)- 12 with a lymphocytosis, hemoglobin (Hgb)-11.4 g/dl, and platelets- 56 k/ul. The patient was referred for recommendations regarding further management.
The physical examination showed the patient to be an 80-year-old white man appearing younger than his stated age. He was in no acute distress and his vital signs were stable. No adenopathy was appreciated. The abdominal exam was significant for 3 large scars from prior surgeries. The extremities had no clubbing cyanosis or edema. CBC revealed: WBC- 10.9 k/ul , Hgb- 11.4 g/dl, hematocrit (Hct)- 33.8%, and platelets- 65 k/ml. Machine-generated differential showed 12% neutrophils, 56% lymphocytes, 11% monocytes, 3% eosinophils, and 28% miscellaneous cells (Figure 1). Review of the peripheral smear revealed the miscellaneous cells to be hairy cells (Figure 2). Nucleated red blood cells (RBCs) were also noted. A comprehensive chemistry profile was obtained: Na- 144 mEq/L, K- 4.5 mEq/L, Cl- 107 mEq/L, CO2- 31 mEq/L, BUN-29 mg/dl, and creatinine 1.2 mg/dl.
A bone marrow aspiration and biopsy were performed. The aspiration revealed a hypocellular marrow with approximately 30% hairy cells (Figure 3 and Figure 4). These cells had oval to reniform nuclei with abundant light blue cytoplasm marked by characteristic projections. Flow cytometry showed that the cells expressed both CD19 and CD11c (Figure 4a).The biopsy also demonstrated involvement with hairy cells although some areas of trilineage hematopoiesis were noted (Figure 5). The patient's diagnosis of HCL was confirmed by the laboratory findings. The worsening picture in the peripheral blood was thought to be secondary to progression of the underlying disease. Treatment options were discussed. The patient elected to undergo therapy with 2-CDA.
Sex
Male
Age
80
Ethnicity
n/a
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Diagnosis
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Hairy cell leukemia (HCL)
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Discussion
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Hairy cell leukemia (HCL) is a rare chronic lymphoproliferative disorder of B-cell lineage. Patients generally present with cytopenias accompanied by significant splenomegaly. Lymphadenopathy is rare and osseous involvement has been described. Vasculitis, arthritis, and nephrotic syndrome have been associated with hairy cell leukemia. Patients may present with opportunistic infections resulting from the profound immunosuppression.
The malignant cells in HCL have a characteristic appearance with a round to oval nucleus, and abundant cytoplasm with thin, hair-like projections which emanate from the perimeter. Alternatively, these cells may appear to have a shaggy outline. Despite this distinctive appearance, the diagnosis of HCL may be problematic. The presence of hairy cells in the peripheral blood is variable. Bone marrow aspiration may be difficult, resulting in a dry tap. This may be secondary to the reticular fibrosis which accompanies hairy cell infiltration of the bone marrow. In such cases, the biopsy assumes primary importance in making the diagnosis. Classic descriptions of the biopsy findings in HCL have described a fried egg appearance: wide spacing of round to ovoid nuclei with clear cytoplasm.
Cytochemistry is useful in distinguishing HCL from other lymphoproliferative disorders. Tartrate resistant acid phosphatase (TRAP) positivity is consistently found in HCL. Immunophenotyping reveals that hairy cells are positive for pan B markers CD19, CD20, and CD22. Expression of CD103 and CD11c help delineate HCL from other lymphoproliferative disorders. FMC7 and CD25 positivity are also common. Cytogenetic analysis may reveal abnormalities of chromosomes 5, 7, and 14. Molecular analysis confirms the B-cell lineage of this disorder by demonstrating rearrangement of the immunoglobulin heavy chains.
Although HCL can be indolent, progressive cytopenia, presence of constitutional symptoms, or recurrent infections require that therapy be started. Historically, splenectomy and an interferon had been used. These modalities have been replaced by the purine analogs, 2-chlorodeoxyadenosine or 2-deoxycorfomycin. Response rates have ranged from 65% to 90%. The responses are generally durable. Although there is no difference in long-term survival between 2-CDA and pentostatin, most physicians prefer 2-CDA given that similar outcomes can be achieved with an abbreviated course of therapy.
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Differential Diagnosis
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Chronic idiopathic myelofibrosis, splenic lymphoma with villous lymphocytes, marginal zone lymphomas, other chronic lymphoproliferative disorders.
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Chapter 12: Lymphoproliferative disorders
Copyright © 2001 by the American Society of Hematology.
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Clinical Summary
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