[Severe hypereosinophilia as a paraneoplastic syndrome in a patient with differentiated thyroid cancer].

In solid tumors, hypereosinophilia is a rare phenomenon and is mainly associated with mucin-secreting carcinomas. Thyroid tumors associated with neutrophilia and/or eosinophilia have been described exclusively in patients with anaplastic thyroid cancer. Eosinophilia associated with papillary thyroid cancer is extremely rare and there are very few cases currently described. It has been suggested that three cytokines, namely interleukin-3 (IL-3), interleukin-5 (IL-5), and granulocyte-macrophage colony-stimulating factor (GM-CSF), may act as a peptide potential eosinophilic. To date, only three patients with differentiated thyroid cancer associated with eosinophilia have been reported, two of the papillary type and one of the medullary type. A 48-year-old patient consulted in 2022 due to bilateral cervical lymphadenopathy of 3 years' duration associated with wasting syndrome and hypereosinophilia. PET CT was requested, which showed hypermetabolic focus in the right thyroid lobe and lymph node, lung, bone, and liver metastases; Thyroid ultrasound showing a nodule of high suspicion of malignancy and a conglomerate of lymphadenopathy in the right lobe with positive needle wash for thyroglobulin. Hypereosinophilia was evaluated with initial leukocytosis values of GB 30,310/mm3 (10,608/mm3 of eosinophils) to maximum values of GB 77,090/mm3 (eosinophils 20,814/mm3). It was interpreted as paraneoplastic syndrome and corticosteroid therapy was started at immunosuppressive doses without response. Our observations presented in this article are in line with most studies reflecting that paraneoplastic hypereosinophilia is characterized by more advanced disease and poor prognosis.