Anaplastic Thyroid Carcinoma: Rare Clinical Case of Extrathyroidal Primary Retroperitoneal Tumour and Review of Literature

Anaplastic thyroid carcinoma is a very rare type of undifferentiated thyroid carcinoma. Mostly, the ATC is diagnosed in advanced stage when local and distant metastases are detected. Multimodal approach and personal treatment managed by a multidisciplinary team of specialist is recommended in all ATC cases. Despite new treatment methods this type of cancer has a very poor prognosis due to fast growth and invasiveness, airway problems and failures of distant metastases control. We present a very rare case of occurrence of anaplastic thyroid carcinoma in the extrathyroidal area. Primary fast growing retroperitoneal tumor with differentiation of anaplastic thyroid carcinoma was diagnosed to a 72-year-old female when no changes were detected in thyroid glands. Due to severe patient status, abdominal pain, and mass effect on surrounding organs caused by suspected retroperitoneal tumor urgent resection surgery was performed. Histopathology analysis confirmed diagnosis of primary retroperitoneal cancer with differentiation of anaplastic thyroid cancer. Later suspected metastases in the left subclavicular lymph node were found but the patient refused further investigation and treatment. Even though the patient is still alive more than 2 years after initial diagnosis and represents a better survival than is described in the literature.