Cytological diagnosis of Spindle Epithelial Tumor with Thymus-like Differentiation (SETTLE)

Spindle epithelial tumor with thymus like differentiation (SETTLE) is a very rare tumor arising either from ectopic thymus or remnants of branchial pouches that retain the potential to differentiate along the thymic line.[1]; Herein is reported a case of SETTLE in a 50-year-old man who presented with dessiminated intravascular coagulopathy. The subsequent work up revealed the presence of a mediastinal mass. A presumptive clinical diagnosis of lymphoma was made, forwhich the patient received a single dose of radiation. The patient’s condition detriorated andnpatient died 5 days later. At autopsy, a thyroid mass of 10x8 cm was found with necrotic friable yellow tan color, extending into the mediastinum, obstructing the superior vena cava with extension into the right atrium and right ventricle forming a hemorrhagic mass of 12x7x6 cm. A touch preparation from the thyroid lesion demonstrated a biphasic lesion consisting of spindle and epithelial glandular components. The tissue specimen from the case demonstrated the spindle cells to stain positively for cytokeratin and vimentin but were negative for thyroglobulin and calcitonin as well as other neuroendocrine markers confirming the diagnosis of SETTLE.