chloroma
Meaning of chloroma: A solid lump made of leukemia cells growing outside the marrow, which can appear before anything abnormal shows up in the blood.
Definition of chloroma
A chloroma is a solid tumor formed by immature myeloid white blood cells collecting in tissue outside the bone marrow, most often in skin, bone, the gum, the eye socket or a lymph node. The old name records its color, since cut surfaces frequently look green. Pathology reports now usually call it a myeloid sarcoma, because a substantial share are not green at all.
Why is it green?
Immature myeloid cells are packed with granules holding an enzyme called myeloperoxidase, which is green, and a mass built almost entirely of such cells takes on that color when it is cut. The color is unstable: on exposure to air it fades within minutes toward pink or gray. That unreliability, together with the many tumors that never look green, is why naming the lesion after its appearance was abandoned in favor of naming it after the cell it is made of.
When does it appear?
| Timing | What it indicates |
|---|---|
| Before any blood abnormality | Leukemia presenting outside the marrow |
| Alongside a new diagnosis | Disease already spread beyond the marrow |
| At relapse after treatment | A site the treatment reached poorly |
| In a long-standing marrow disorder | Transformation toward acute disease |
The first row is the one that causes diagnostic trouble. A lump in the orbit or under the skin, with an unremarkable blood count, gets biopsied as an unknown tumor and is readily mistaken for a lymphoma under the microscope, since both are sheets of small round cells. Staining for myeloid markers separates them.
What does it mean for the disease as a whole?
It is treated as a systemic problem rather than a local one. Even where marrow and blood look normal, the lesion is regarded as acute myeloid leukemia that happens to have surfaced in tissue, so management follows leukemia treatment rather than surgery or radiation to the lump alone. The same lesion is a recognized way for chronic myeloid leukemia to announce that it has entered a more aggressive phase. Older writing calls it a granulocytic sarcoma, and all three names describe one entity.
Also known as
Used in a sentence
Biopsy of the orbital mass showed a chloroma preceding any marrow abnormality.
Good to know
An isolated chloroma with a normal blood count is regarded as acute myeloid leukemia presenting outside the marrow rather than as a localized tumor, and biopsy material resembles lymphoma closely unless myeloid markers are stained for.
Word origin
Where “chloroma” comes from
Greek chloros, meaning green, with the ending -oma, which marks a tumor or swelling.