Orbital Chloroma

All content on Eyewiki is protected by copyright law and the Terms of Service. This content may not be reproduced, copied, or put into any artificial intelligence program, including large language and generative AI models, without permission from the Academy.

Article initiated by:

Dr. Aparna. M, MD

All contributors:

Dr. Aparna. M, MD, Paul Phelps, MD, FACS, Jill Wells, MD, Michael T Yen, MD, Dr. Aparna. M, MD, Christina H. Choe, MD

Assigned editor:

Christina H. Choe, MD

Review:

Assigned status Up to Date

 by Christina H. Choe, MD on July 12, 2026.

add
Contributing Editors:	add

Disease Entity

Orbital myeloid sarcoma / chloroma

Disease

Myeloid sarcoma (MS), also known as chloroma, is an extramedullary solid tumor that is caused by an abnormal proliferation of immature precursors of white blood cells. In 1811, a British physician Alan Burns observed the first case of chloroma. In 1853, King coined the term chloroma due to its greenish hue secondary to the presence of intracellular myeloperoxidase enzyme. In 1966 chloroma was renamed granulocytic sarcoma by Rappaport. Granulocytic sarcoma had many synonyms including myeloblastoma, myelocytoma, chloroleukaemia, and the World Health Organization currently favors the name myeloid sarcoma.

Ocular structures can be involved in AML via two distinct mechanisms. Direct infiltration of leukemic cells may occur as anterior segment uveal infiltration, orbital infiltration, or central nervous system (CNS) involvement with neuro-ophthalmic signs which is known as primary involvement . Hematologic abnormalities seen in leukemia leads to secondary involvement. Anemia and thrombocytopenia can produce tissue ischemia and hemorrhage, while leukostasis and immunosuppression may predispose to occlusion injury and infection, respectively.

Epidemiology

Orbital involvement of MS is uncommon and primary orbital presentation without any evidence of systemic involvement is rare. Even less common is the isolated presentation MS in the eyelid. MS may develop at any age even though nearly 60 % of cases are seen in children under 15 years of age with a median age of 7 years old. MS-associated AML is more frequently seen in boys than girls. In the pediatric population, acute leukemias account for about 30 % of the malignancies in which acute myeloid leukemia accounts for about 15 %. MS is indeed a rare disease that is often related to other underlying myeloproliferative disorders. In patients with acute myeloid leukemia, MS is a rare manifestation that may occur in around 2.5-9.1 % of patients. Less frequently, it may be associated with chronic myeloid leukemia with impending blast crisis or other myelodysplastic disorders like myeloid metaplasia, polycythemia vera, hypereosinophilic syndrome, or essential thrombocytosis. The orbit is one of the most common sites of occurrences in the pediatric population. Rarely it may occur in lymphoid leukemia also.

MS is thought to originate in the bone marrow, the cells being spread through the Haversian canals to penetrate the sub periosteum to form soft tissue masses which explains the typical location near bone structures. These neoplasms are identified in the orbit in 9.3% of cases. Active hematopoiesis leads to proptosis in one or both eyes.

Classification

Audoin et al have described the following patterns:

1. Concurrent with AML: this is the most common manifestation and may be present at the time of initial presentation or occur any time during the active phase of AML.
2. Relapse: it may present after AML remission, especially in bone marrow transplant recipients. This is considered a systemic disease despite normal blood counts and marrow findings.
3. The precursor of blast phase transformation: In non-leukemic myeloproliferative conditions, development of MS heralds a blast crisis and subsequent AML transformation.
4. Primary chloroma: this is a rare nonleukemic form, occurring in otherwise healthy individuals in the absence of any marrow abnormality. Primary chloroma may precede any hematological abnormality in nearly 35 % of cases.it may undergo a leukemic transformation in an average interval of 10 months.

Risk Factors

Certain types of AML predispose the individual to develop myeloid sarcoma, including AML M4 /M5 (French American-British classification). Other risk factors include high peripheral total leukocyte counts, chromosomal abnormalities t (8,21) or inv (16), myeloblasts expressing T cell markers like CD 13, CD 14.

Diagnosis

Clinical Features and Differential Diagnosis

Correct diagnosis of orbital myeloid sarcoma is quite difficult sometimes owing to its uncommon presentation and mimickers during clinical and radiological examination.

When MS presents as an isolated finding, which is very rare, it may mimic inflammation, infection or lymphoproliferative diseases, vascular lesion, lymphoma, metastatic neuroblastoma, and rhabdomyosarcoma. Radiological examination may pave the way for the right diagnosis. MS can be asymptomatic, present with eyelid swelling mimicking preseptal cellulitis, or most commonly present with proptosis. Zimmerman et al noted that 88% of their patients presented with proptosis, most commonly unilateral but can also be bilateral (one case report also noted bitemporal swelling). Other causes of acute bilateral proptosis in children include bilateral optic nerve glioma, orbital extension of retinoblastoma, and cavernous sinus thrombosis.

Proptosis may occur due to leukemic infiltrates, retrobulbar hemorrhage, orbital muscle infiltration, or venous blockage. Other presentations of MS include painful lacrimal swelling, conjunctival mass lesion, lacrimal gland swelling, retinal hemorrhages, ptosis, iris and uveal alterations, and dystopia. Decreased visual acuity and ocular movement restriction have been reported in the majority of cases.

In cases of isolated MS, acute leukemia may develop shortly afterward with a median time ranging from 1-25 months. Therefore isolated MS should be treated as the initial manifestation of acute leukemia as such rather than a localized lesion. Shields et al have reported that about 88 % of cases with proptosis that are seen by ophthalmologist do not have a history of leukemia at the time of presentation and an estimate of 60% of orbital sarcoma being bilateral. The diagnosis of orbital MS becomes easier when the patient is already a known case of hematological malignancy or when there are associated symptoms like epistaxis and other systemic features suggestive of malignancies.

Diagnostic Procedures

1. Peripheral smear: it is an invaluable tool in diagnosing the systemic disease which may show immature blast cells with a high total leukocyte count and relative neutropenia.
2. Bone marrow biopsy: sometimes MS may not be associated with peripheral smear abnormality; hence bone marrow aspirate and biopsy can be done to confirm AML based on finding greater than 30 % myeloid blast cells.
3. Radiological imaging: since MS is a soft tissue tumor that may be circumscribed or diffusely infiltrating, CT findings may be variable. Lesions in the orbit are frequently hypodense with mild enhancement. Sometimes it can present with heterogeneous enhancement with non-enhancing areas that represent necrosis and sign of rapid growth. On MRI, MS lesions are isointense or hypointense on T1 weighted and mildly hyperintense on T2 weighted images. MRI can also be useful for follow-up imaging as, unlike CT scans, there is no concerns for radiation exposure. Nuclear imaging like FDG-PET/CT and gallium 67 shows avid uptake by MS, which can be used to decipher the multiplicity as well as a response after chemotherapy. FDG-PET is imperative in radiotherapy planning. But despite all these imaging, MS can be confused with lymphoma, which is a much more common malignancy.
4. Immunohistochemistry: confirmation of MS is established on immunohistochemistry after the demonstration of monoclonal antibodies against specific antigens. The most widely used are CD43, CD68, and lysozyme. Specific cytochemical stains for diagnostic purposes as per WHO classification (2008) are chloroacetate esterase, myeloperoxidase, and nonspecific esterase. Other markers are CD33, CD34, CD4, CD56, or CD 117 depending on maturation and lineage of myeloid cells. MPO, lysozyme, and CD68 are the most sensitive markers for myeloid differentiation.

Management

General Treatment

There is no current consensus on the best therapy due to the rarity of the MS. Orbital MS has been generally thought to be an antecedent event to the evolution of AML, and treatment options are customized to the individual patient. Therapeutic options include surgery, radiotherapy, and chemotherapy. Given the systemic nature of AML, chemotherapy is the mainstay of management in most cases.

Isolated orbital MS in AML remission and primary isolated MS are generally considered systemic diseases and are often treated along the lines of AML even when the peripheral blood smear is within normal limits. MS associated with myelodysplastic syndromes also warrant systemic chemotherapy because of suggested leukemic transformation.

Lee et al studied patients with isolated MS who had undergone only local treatment and found out that 22.2% of them did not progress to AML. Among those who were treated with surgery alone, patients achieved complete remission duration of 1.8 months and among those who received radiotherapy, a remission duration of 83.9 months was achieved. In contrast, 44.4% who received systemic chemotherapy evolved to AML within a median time of 13.4 months. A review of 20 cases of nonleukemic MS reported that combined treatment with chemotherapy and radiotherapy had better survival than chemotherapy alone. Hence surgery or radiotherapy may play an important role in controlling the primary disease without much toxicity and evolution into the systemic disease. However, combining systemic and local treatment for isolated orbital MS will be a more promising therapeutic strategy to achieve complete remission of the systemic disease than a single treatment modality alone. If the MS persists after completion of induction therapy, local treatment such as surgery and radiotherapy may be considered. Chemotherapy includes both an intensive and consolidated phase. Doxorubicin and cytosine arabinoside is used for the intensive phase. Bone marrow suppression is strictly monitored and allogenic hematopoietic cell transplantation is another therapeutic option for systemic disease.

Prognosis

The detection of MS is considered evidence that the premalignant conditions have transformed into an acute phase. As such, presence of MS may be sufficient to indicate that chronic myelogenous leukemia has entered its blast crisis. When it occurs during relapse after successful treatment of disease, it can be regarded as the early sign of systemic relapse. A review in which 24 patients who developed isolated MS after treatment for AML has reported that the mean interval until bone marrow relapse to be 7 months. On average, the median survival after diagnosis is 7.5 months for MS. Age, gender, or underlying systemic disease does not affect the prognosis of the disease. Since the emergence of new treatment options for leukemia like allogenic bone marrow transplantation, repeated donor lymphocyte infusion the longevity of patients has increased thus increasing the incidence of MS. Even after aggressive involvement due to their high responsiveness to induction chemotherapy, timely diagnosis is warranted.