Amelia is 32 years old and presents with a 1 week history of a left sided neck lump she discovered whilst applying suncream. It has not grown and is not painful. Past medical history includes Hypothyroidism and she is stable on 50mcg Levothyroxine daily.
On examination, you observe a 2cm soft skin coloured nodule in the left anterior triangle. The overlying skin looks normal and you are able to move it beneath the surface.
What is the most likely diagnosis?