| Summary: | ABSTRACT: Objective: In contrast to well-differentiated and anaplastic thyroid carcinomas, metastasis patterns are not well-known for poorly differentiated thyroid carcinoma (PDTC). We report an unusual case of PDTC initially presenting as unilateral exophthalmos.Methods: Clinical, laboratory, imaging, and pathology data are presented.Results: A 55-year-old woman without significant medical history presented to an outside hospital complaining of a “bulging” left eye for several weeks. Computerized tomography–guided excisional biopsy of a left orbital mass revealed poorly differentiated insular thyroid carcinoma (positive for cytokeratins, thyroid transcription factor-1, and thyroglobulin; negative for monoclonal carcinoembryonic antigen, S100, chromogranin, and synaptophysin) with a Ki-67 index of 5 to 10%. In the midst of outpatient management, including treatment with dexamethasone, she presented to our tertiary center in diabetic ketoacidosis. Physical examination demonstrated unilateral left-sided exophthalmos and an unremarkable thyroid gland. Brain magnetic resonance imaging confirmed an exophytic mass centered on the wing of the left sphenoid bone with intracranial and intra-orbital extension. Thyroid ultrasound demonstrated a dominant hypoechoic nodule in the right lobe with possible punctate microcalcifications; fine needle aspiration confirmed PDTC. Neurosurgery was recommended but the patient declined. Following outpatient radiation to the left orbit, she was readmitted for dyspnea on exertion due to new bilateral pulmonary emboli. The patient was no longer a candidate for thyroidectomy and was referred for home hospice services.Conclusion: PDTC is a relatively new entity with poorly defined patterns of metastasis. We present the first reported case of PDTC with metastasis to the orbit initially presenting as unilateral exophthalmos.Abbreviations: FTC = follicular thyroid carcinoma; PDTC = poorly differentiated thyroid carcinoma; WBI = whole-body iodine
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