Juxtathyroidal neck soft tissue angiosarcoma presenting as an undifferentiated thyroid carcinoma.

Angiosarcoma is a malignant growth of endothelial origin, uncommon in the head and neck. We present the case of a 38-year-old woman with long-standing goiter who presented with a rapidly growing 6.0-cm neck mass. Fine-needle aspiration biopsy of the tumor showed features of "undifferentiated thyroid carcinoma (ThyrCa)." Total thyroidectomy resulted in extirpation of all gross disease. Pathology revealed a high-grade angiosarcoma of the neck invading the thyroid gland, coexisting with papillary ThyrCa (follicular variant) in the contralateral lobe. Aggressive external electron beam radiotherapy was initiated for local control. Despite the absence of systemic dissemination initially, bulky neck recurrences, and pulmonary metastases developed rapidly, leading to the patient's demise on postoperative day 41. Autopsy showed metastatic disease involving most organs. This case illustrates that neck angiosarcomas need to be considered in the differential diagnosis of "poorly differentiated" thyroid malignancies. These soft tissue neck tumors may complicate postoperative management due to their bleeding tendency and aggressive infiltrative behavior, and carry a dismal prognosis because of the rapidity of development of local recurrence and distant metastases.