Excessive Leukocytosis Leading to a Diagnosis of Aggressive Thyroid Anaplastic Carcinoma: A Case Report and Relevant Review

Introduction Leukocytosis and particularly neutrophilia are usually caused by acute infection, inflammation, and myeloproliferative neoplasms. However, leukocytosis can also occur in patients with malignancy either due to bone marrow metastases or in the context of a paraneoplastic syndrome. Case Presentation An 86-year-old female was admitted to our hospital due to marked leukocytosis (white blood cells [WBC] >40,000/μL), neutrophilia, and monocytosis. She was afebrile and reported hoarseness and mild difficulty swallowing. Upon physical examination, lung auscultation revealed inspiratory wheezing and a non-tender mass was observed in the anterior midline of the neck. Blasts and immature WBC were not found, and polymerase chain reaction for the detection of BCR/ABL gene was negative. A mass (5.4 cm in diameter) of abnormal parenchymal composition with calcifications occupying the right lobe, was seen on thyroid ultrasound. Cytology, after fine-needle aspiration, showed an anaplastic thyroid carcinoma (ATC). The cervical and chest computed tomography scan revealed a low-density lesion with calcifications that shifts and presses the trachea and multiple lung nodular lesions bilaterally. Since the case was inoperable and the airway was severely obstructed, a DUMON stent was placed. Biopsy of specimens from the trachea lesion revealed a tumor with significant atypical cells and focal squamoid features. The patient's WBC increased to 72,470/μL. Additionally, interleukin-6 (IL-6) was markedly elevated (20.2 pg/mL). The patient passed away due to respiratory arrest 55 days after her initial admission. Discussion Excessive leukocytosis in a patient, having excluded infectious disease and myelodysplastic syndrome, could represent a manifestation of a paraneoplastic syndrome due to various cytokines secretion from the tumor. In our case, ATC synthesized and secreted IL-6, which seems to be the cause of severe leukocytosis.