The mechanism is not entirely clear. T-cells are normally involved in activation of eosinophils and it is possible that malignant lymhocytes begin to produce factors with stimulatory activity on eosinophils 16. Cells like neutrophils are sometimes also activated. Release of substances from necrotic tumor tissue has also been suggested to be involved 6,11. Stromal invasion of the peritumoral tissue and the tumor itself is seen in cases with blood eosinophilia but can occur independently as well 11.
Cervical cancer is the most common malignancy causing tissue invasion by eosinophils.
It has been described also in adenocarcinomas of the gastrointestinal or urogenital tract as well as in all the tumors causing blood eosinophilia. Contrary to the blood eosinophilia stromal invasion is generally believed to be a sign of good prognosis. These tumors seemed to be histologically different from malignancies without eosinophil infiltration. Another study confirmed this observation, indicating that eosinophilia is a specific reaction to some tumors 26 . It is not known if viral infection plays a role.