Eosinophilia may be found in a patient with an underlying non-myeloid malignancy as a major or incidental finding. Most cases of eosinophilia associated with an underlying malignancy have been reported in myeloid neoplasms, but eosinophilia can occur with lymphoid tumors and solid carcinomas as well.
Hypereosinophilia indicates a persistent absolute eosinophil count >= 1,500 per µL.
Mechanisms of the eosinophilia:
(1) release of interleukins that stimulate production of eosinophils (IL-3, IL-5) from T-cells or tumor cells
(2) tumor release of G-CSF or GM-CSF (granulocyte colony stimulating factor)
(3) nonspecific leukemoid reaction
(4) reaction to drug or infection
Non-myeloid hematologic malignancies associated with eosinophilia:
(1) B-cell or T-cell lymphoma
(2) Hodgkin's disease
(3) acute lymphoblastic leukemia
Carcinomas associated with malignancy:
(1) breast
(2) lung
(3) renal cell
(4) hepatocellular
(5) malignant melanoma
(6) thyroid
(7) gastric
(8) anaplastic carcinoma of unknown primary
(9) pancreatic adenocarcinoma
When directly associated with the tumor, the level of eosinophilia corresponds with tumor load (high when progressing, low in remission).
