Anaplastic carcinoma is one of the most aggressive forms of cancer, and in the context of sonography, it is most commonly encountered in the thyroid gland. On ultrasound, an anaplastic thyroid carcinoma typically appears as a large, irregular, hypoechoic mass that often invades surrounding structures like the trachea, esophagus, and neck muscles. Unlike slower-growing thyroid cancers, anaplastic carcinoma tends to grow very rapidly over weeks, and patients often present with a quickly enlarging neck mass and difficulty swallowing or breathing. This type of cancer accounts for less than 2 percent of all thyroid cancers but is responsible for a disproportionate number of thyroid cancer deaths.
Sonography Term