Ophthalmologic Manifestations of Leukemias Workup

Updated: Mar 10, 2017
  • Author: Lihteh Wu, MD; Chief Editor: Hampton Roy, Sr, MD  more...
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Workup

Laboratory Studies

CBC and differential

CBC is the most useful initial laboratory test in patients suspected of having leukemia. Most patients will show some abnormality in the CBC and some blasts will be seen in the peripheral smear in patients with acute leukemias.

To diagnose CLL, a lymphocytosis of greater than 5000/mm3 must be present. The absolute neutrophil count is usually normal (see the Absolute Neutrophil Count calculator) and red blood cell counts and platelet counts are mildly decreased. In addition, the peripheral smear or bone marrow should show normal mature small lymphocytes with less than 55% atypical or blast forms.

CML is defined by its peripheral WBC count. Typically, leukocytosis is in excess of 100,000/mm3. The differential count shows that neutrophil precursors are present. This is accompanied by basophilia and eosinophilia. Unlike those in AML, these cells are mature and functional.

Bone marrow aspiration

Bone marrow aspiration establishes the diagnosis of leukemia. The morphology of blasts usually can differentiate between ALL and AML.

In ALL, a homogeneous infiltrate of lymphoblasts replaces the normal bone marrow elements. Lymphoblasts usually are small and measure approximately 14 µm in diameter. They have scant cytoplasm with no granules. The nucleus has no nucleoli or a small indistinct one.

For the diagnosis of AML, 30% of the nucleated cells in the aspirate must be blast cells of myeloid origin. Multiple large nucleoli, delicate chromatin, gray-blue cytoplasm, and Auer rods characterize myeloblasts. The presence of Auer rods is virtually diagnostic of AML, because these condensed lysosomal cytoplasmic azurophilic rod-shaped structures do not appear in ALL.

In CLL, bone marrow infiltration exceeds 30% lymphocytes. The lymphocytes are mature with less than 55% atypical or blast forms. The nuclei are round, cytoplasm is scant, chromatin is compact, nucleoli are inconspicuous, and mitotic figures are rare.

Immunophenotyping

Immunophenotyping using multiparameter flow cytometry following labeling with monoclonal antibodies to cell-surface antigens identifies the B or T cell origin of the lymphoblasts.

Based on the expression of B lineage-restricted antigens and clonal rearrangements of immunoglobulin heavy and light chain genes, it has been estimated that up to 80% of ALL cases arise from B-cell precursors. The majority possesses a common ALL antigen (CALLA) that is present only on leukemic cells.

T-cell ALL possesses receptors for sheep erythrocytes, and, when these are combined, they form E-rosettes.

A final subset of ALL lacks B- or T-cell characteristics and is referred to as null-cell ALL.

Certain myeloid-specific antigens, such as CD13, CD33, and CD41, have been used to diagnose AML.

The malignant cells in CLL correspond to a minor subpopulation of B cells that express cell surface immunoglobulin M (IgM) and immunoglobulin D (IgD) and the T-cell associated antigen CD5.

Histochemical stains

Histochemical stains for myeloperoxidase (Leder stain) and nonspecific esterase have a strong affinity for myelogenous precursors but fail to stain lymphocytic forerunners.

Demonstration of nuclear DNA polymerizing enzyme terminal deoxynucleotidyl transferase (TdT) is indicative of a lymphoid origin. However, up to 2-5% of patients with AML exhibit this enzyme. Exceptions may occur when a malignant clone arises from multipotent cells that may express both myelogenous characteristics and lymphocytic characteristics.

Chromosomal analysis

Chromosomal analysis also plays an important role. The diagnosis of CML is established by identifying cytogenetically or molecularly a clonal expansion of a hematopoietic stem cell possessing a reciprocal translocation between chromosomes 9 and 22.

Chromosomal analysis of the leukemic cell currently provides the most important pretreatment prognostic information in AML.

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Imaging Studies

Fluorescein angiography may reveal myriad diffuse leakage points at the level of the RPE. This pattern also may be seen in Vogt-Koyanagi-Harada disease, diffuse choroidal melanoma, metastatic tumors, and posterior scleritis.

Optical coherence tomography (OCT) can help confirm the diagnosis of macular exudative detachment. OCT can also be useful in monitoring patients following treatment.

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Histologic Findings

Histopathological studies have shown the choroid to be the ocular structure most commonly involved by leukemia. The choroid is thickened, especially at the posterior pole. The RPE may be hyperplastic, atrophied, or hypertrophied. Photoreceptor loss, drusen formation, serous detachment, and cystoid retinal edema may be present.

Immature white blood cells infiltrate the retina, and, when they accumulate, nodular masses may be seen. The retinal vessels usually are packed with immature leukocytes. Capillary nonperfusion may result due to massive accumulation of cells. Diffuse infiltration of the iris and the ciliary body is commonly seen. The infiltrates are usually denser near the sphincter and the base of the iris. The trabecular meshwork may be clogged with leukemic cells leading to glaucoma.

Histopathological studies indicate that leukemic infiltration in the orbit most often was mild and diffuse as opposed to massive and tumorous. A chloroma of the orbit is composed of immature granulocyte cells, which contain large amounts of the enzyme myeloperoxidase, giving the tumor a greenish hue on gross examination. Because of the poorly differentiated nature of this tumor on histological examination and often unremarkable CBC, it may be misdiagnosed as a lymphoma.

Histological diagnosis of lymphoma in a rapidly growing orbital mass of a child is unlikely because orbital lymphomas in children are quite rare.

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