Editing Myeloid sarcoma (section)

== Types ==

=== In acute leukemia ===
Chloromas are rare; exact estimates of their prevalence are lacking, but they are uncommonly seen even by physicians specializing in the treatment of [[leukemia]]. Chloromas may be somewhat more common in patients with the following disease features:<ref name="review">{{cite journal |vauthors=Byrd JC, Edenfield WJ, Shields DJ, Dawson NA |title=Extramedullary myeloid cell tumors in acute nonlymphocytic leukemia: a clinical review |journal=J. Clin. Oncol. |volume=13 |issue=7 |pages=1800–16 |date=July 1995 |pmid=7602369 |doi=10.1200/JCO.1995.13.7.1800 }}</ref>
* [[French–American–British classification|French–American–British (FAB) classification]] class M2
* WHO Classification (2016 revision) is a separate entity under the "Acute myeloid leukemia (AML) and related neoplasms"
* those with specific [[cytogenetics|cytogenetic]] abnormalities (e.g. t(8;21) or inv(16))
* those whose [[myeloblast]]s express [[T-cell]] surface markers, [[CD13]], or [[CD14]]
* those with high peripheral [[white blood cell]] counts

However, even in patients with the above risk factors, chloroma remains an uncommon complication of acute myeloid leukemia.

Rarely, a chloroma can develop as the sole manifestation of relapse after apparently successful treatment of acute myeloid leukemia. In keeping with the general behavior of chloromas, such an event must be regarded as an early herald of a systemic relapse, rather than as a localized process. In one review of 24 patients who developed isolated chloromas after treatment for acute myeloid leukemia, the mean interval until bone marrow relapse was 7 months (range, 1 to 19 months).<ref>{{cite journal |vauthors=Byrd JC, Weiss RB |title=Recurrent granulocytic sarcoma. An unusual variation of acute myelogenous leukemia associated with 8;21 chromosomal translocation and blast expression of the neural cell adhesion molecule |journal=Cancer |volume=73 |issue=8 |pages=2107–12 |date=April 1994 |pmid=7512442 |doi=10.1002/1097-0142(19940415)73:8<2107::AID-CNCR2820730815>3.0.CO;2-W|doi-access=free }}</ref>

=== In myeloproliferative or myelodysplastic syndromes ===
Chloromas may occur in patients with a diagnosis of [[myelodysplastic syndrome]] (MDS) or [[myeloproliferative syndrome]]s (MPS) (e.g. [[chronic myelogenous leukemia]] (CML), [[polycythemia vera]], [[essential thrombocytosis]], or [[myelofibrosis]]). The detection of a chloroma is considered ''de facto'' evidence these premalignant conditions have transformed into an acute leukemia requiring appropriate treatment. For example, presence of a chloroma is sufficient to indicate chronic myelogenous leukemia has entered its 'blast crisis' phase.

=== In eosinophilic leukemia ===
At least one case of [[FIP1L1#FIP1L1-PDGFRA|''FIP1L1-PDGFRA'']] fusion gene-induced eosinophilic leukemia presenting with myeloid sarcoma and eosinophilia has been reported. This form of myeloid sarcoma is distinguished by its highly successful treatment with [[imatinib]] (the recommended treatment for ''FIP1L1-PDGRGA'' fusion gene-induced eosinophilic leukemia) rather than more aggressive and toxic therapy.<ref name="pmid26276769">{{cite journal | vauthors = Vega F, Medeiros LJ, Bueso-Ramos CE, Arboleda P, Miranda RN | title = Hematolymphoid neoplasms associated with rearrangements of PDGFRA, PDGFRB, and FGFR1 | journal = American Journal of Clinical Pathology | volume = 144 | issue = 3 | pages = 377–92 | year = 2015 | pmid = 26276769 | doi = 10.1309/AJCPMORR5Z2IKCEM | s2cid = 10435391 | doi-access = free }}</ref>

=== Primary chloroma ===
Very rarely, chloroma can occur without a known pre-existing or concomitant diagnosis of acute leukemia, [[acute promyelocytic leukemia]] or MDS/MPS; this is known as primary chloroma. Diagnosis is particularly challenging in this situation (see below). In almost all reported cases of primary chloroma, acute leukemia has developed shortly afterward (median time to development of acute leukemia 7 months, range 1–25 months).<ref name="review"/> Therefore, primary chloroma could be considered an initial manifestation of acute leukemia, rather than a localized process, and could be treated as such. Where disease development or markers indicate progresses to acute promyleocytic leukemia (AML3) treatment should be tailored to this form of disease.