Chloroma is a rare, malignant tumor made up of granulocyte precursor cells. It is also called granulocytic sarcoma or extramedullary myeloblastoma and is usually associated with myeloblastic leukemia. It is a solid tumor that contains primitive precursors of myeloblasts, promyelocytes, and myelocytes.
Chloroma is usually found in the bones, lungs, CNS, skin, lymph nodes, bowel, and soft tissues in head and neck, and breasts. First described in 1811 by Burns, these immature cells were named chloroma as they appeared green in color probably due to high myeloperoxidase levels. They were renamed as granulocytic sarcoma in the year 1966, when it became clear that they are only partially green and some of the cells appeared gray, brown, or white, depending on the concentrations of cellular enzymes or their state of oxidation.
Granulocytic sarcomas occur in 2.5 - 9.1% of acute myeloid leukemia (AML) patients with acute myelogenous leukemia. While both genders are equally affected by chloromas, children seem to be more affected than adults as 60% of chloroma patients are below 15 years. They can occur during remission or relapse or as a complication of leukemia.
Patients mostly present with a history of AML; but occasionally, in up to 35% of patients, the diagnosis of chloroma occurs without prior AML diagnosis. This makes it tough to differentiate chloroma from lymphoma by radiologic or clinical methods. However, most of these 35% patients go on to develop AML within a couple of years.
Symptoms of Chloroma
In many cases, granulocytic sarcomas cause no major symptoms and about 50% of chloroma cases are diagnosed only during autopsy. The symptoms of chloroma are usually caused by the mass itself or the way it affects the organ on which it is located. Chloroma in the CNS is associated with symptoms such as cauda equina syndrome or radiculopathy.
Radiologic Features of Chloroma
The chloroma masses in soft tissue may be infectious and may consist of hemorrhage, or secondary neoplasms. The earlier the diagnosis, the better, as each complication will need specific therapy. These lesions can be distinguished with the help of imaging findings. CT and MR scans are helpful in identifying chloromas and devising treatment plans.
In patients without prior AML diagnosis, chloromas are usually misdiagnosed as several malignant masses. Though uncommon, it is important to differentiate chloromas and treat them appropriately, as they respond better to focal irradiation than chemotherapy.
Diagnosis and Prognosis
In order to accurately diagnose chloromas, special staining and histochemistry analyses are needed. Chloromas do not negatively affect the prognosis of AML patients as compared to patients without chloromas. However, chloroma in patients with chronic leukemia affects the prognosis negatively. Chloroma is usually sensitive to chemotherapy or irradiation and resolve fully within 3 months, though in about 23% of the patients, it recurs.
Although very rare, any local mass whose etiology is not known should be evaluated thoroughly by orthopedists, especially in AML patients. Knowledge of this possibility can speed up treatment and avoid unnecessary surgeries.
Treatment of Chloroma
Chloromas can be managed through chemotherapy to treat the underlying leukemia. In case of refractory or resistant lesions that do not respond well to chemotherapy, radiation therapy or surgical debridement can be an option. Patients newly diagnosed with AML respond better to chemotherapy than those who present with a relapse.
References
Further Reading
UC's Eric Vick receives major grants to advance research into combination therapy for leukemia