A 35-year old female presented with a swelling in the neck for the past 2 months, she had the treatment for Hodgkin’s lymphoma when she was 22 years with irradiation. On examination, her vitals were normal, there was a single, firm, irregular nodule, moving with deglutition in the left side of midline. Clinical examination also revealed a single node in the left side of the neck. The most likely clinical diagnosis of this condition is: