Orbital leukemia - Clinical Tree

Key points

Definition: Leukemia presenting as an orbital mass portends a more serious prognosis as these patients continue to show significantly lower survival rates than other leukemia patients.
Synonym: A subset of orbital leukemia includes: granulocytic sarcoma, chloroma, or myeloid sarcoma.
Classic clue: An 8-year-old presenting with a sensation of fullness, double vision, and proptosis has a homogeneous extraconal mass that molds to orbital wall without associated bony destruction.
Acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and chronic myeloid leukemia (CML) are the most frequent causes of orbital leukemia.
Orbital leukemic tumors occur most frequently in the first decade as secondary AML. Mean age at diagnosis is 8 years. It also occurs in adults with chronic lymphocytic leukemia (CLL).
Have homogeneous masses, which mold to one or more bony walls without bone marrow destruction.
Advances in leukemia treatment have improved survival, but have also increased the prevalence of patients with orbital involvement.
Some orbital abnormalities are related to side effects from treatment. Others enable the recognition of recurrent leukemia.
Patients with orbital leukemia often have systemic symptoms and a history of leukemia.

Imaging features of orbital leukemia generally fall into three types ^2,4 :

Type I: Involvement of uvea, choroid, retina, and optic nerve (ON).
Optic nerve leukemia (ONL).
The optic nerve (ON) is involved in 13% to 18% of all leukemic types. ^,
Although extremely rare, ALL may present with ONL and lead rapidly to blindness.
ONL may herald hematologic relapse by months.
Diagnosis and treatment of optic nerve leukemia is a true emergency because of the potential for rapid visual decline.
See Chapter 38 : Optic Nerve Leukemia.
Type II: Infiltration of orbital soft tissues.
Usually involves orbital fat and sometimes the lacrimal gland.
Usually appears as homogeneous mass molded against adjacent orbital wall ( Figure 20-1 , A and B ).
Usually does not cause destruction of adjacent bony wall ( Figure 20-1, C and D ).
Type III: Granulocytic sarcoma (GS).
Epicenter in orbital subperiosteal space, usually involves lateral orbital wall.
Involves the orbital subperiosteal space, often causing bone destruction in the absence of peripheral blood involvement.
May extend into temporal and infratemporal fossae. ^,
Lesions located medially may involve ethmoids, cribriform plate, and anterior cranial fossa.
Dural or leptomeningeal involvement may be revealed by contrast enhancement.
Arises along lateral more than medial orbital wall.
Calcification is usually absent.
GS is often a precursor to systemic leukemia. ^,

See General Imaging Features for Types I, II, and III listed earlier.

Type I
See Chapter 38 : Optic Nerve Leukemia.
Type II
Usually appears as relatively dense homogeneously enhancing masses molded against adjacent orbital wall (see Figure 20-1 , A and B ).
Usually does not cause destruction of adjacent bony wall (see Figure 20-1 , C and D ).
Shows mild to moderate enhancement.
Type III: Granulocytic sarcoma
Isodense to extraocular muscles (EOMs).
May cause bony erosion in the absence of peripheral blood involvement.
With epicenter in the orbital subperiosteal space, it usually involves lateral more than medial orbital walls with bone destruction.
May extend into infratemporal and temporal fossae. ^,
Lesions located medially may involve ethmoids, cribriform plate, and anterior cranial fossa.
Contrast enhancement can depict dural or leptomeningeal involvement.
Calcification is usually absent.

Type I
See General Imaging Features for Type I listed earlier.
See Chapter 38 : Optic Nerve Leukemia.
Type II
See General Imaging Features for Type II listed earlier.
They usually appear as homogeneous masses molded against adjacent orbital wall.
They usually do not cause destruction of adjacent bony wall.
The MRI signal characteristics vary depending on histology.
Tend to be hypointense on T1.
They vary from hypointense to hyperintense on T2.
T1 + Gd enhancement is usually homogeneous, but sometimes limited and may be better demonstrated with fat-saturation techniques.
Type III: Granulocytic sarcoma
See General Imaging Features for Type III listed earlier.
Tend to be hypointense on T1.
They vary from hypointense to hyperintense on T2.
T1 + Gd enhancement is usually homogeneous, but sometimes limited and may be better demonstrated with fat-saturation techniques.

Increased osteoblastic activity causes increased uptake on both blood pool and delayed images.
Highly sensitive, but not very specific.
Gallium-67 may require imaging 3 to 4 days after injection.

Patients may present with a sensation of fullness in the eyelid, diplopia, and exophthalmos.
Most patients have a leukemia diagnosis before presenting to an ophthalmologist.
In some patients, ocular manifestation may occur during systemic relapse, or even following complete remission.
Occasionally patients present with an orbital mass as a first sign of AML.

All types of leukemia may affect the orbit, but involvement by ALL is most common.
ALL has morphed from a fundamentally fatal disease to a highly curable one over the last 40 years.
ALL treatment is difficult, demanding, and multifaceted requiring multispecialty management.
∼90% of patients with ALL show some orbital involvement. ^,
Leukemic patients with orbital involvement have significantly lower survival rates.
Ocular involvement usually occurs during the development of illness, but may be a harbinger of postremission relapse. ^,
Every ALL patient should have periodic complete ophthalmologic examinations, starting at diagnosis, to detect any orbital involvement. ^, ^,
ON is involved in 13% to 18% of patients with leukemia.
ONL predicts a very poor prognosis, particularly if occurring while the patient is still receiving treatment. ^,
See Chapter 38 : Optic Nerve Leukemia.

Treatment of orbital leukemia is complicated and must be instituted promptly.
Combinations of radiotherapy and chemotherapy can be complex and regimens vary with disease type and stage.
Timely treatment improves prospects of maintaining some level of vision.
Leukemia treatment is ever-evolving and has constantly changed over the last few years.
Prognosis of orbital leukemia is poor, with a 30% to 40% overall cure rate.
A bone marrow transplant (BMT) from a matched family donor remains the best long-term option.
Involvement of the ON in leukemia is an emergency requiring prompt specialized treatment to salvage some vision.
See Chapter 38 : Optic Nerve Leukemia.

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