The image is from a 26-year-old catering worker, a recent immigrant from the Middle East. He had noticed a lump in the left anterior triangle of his neck about 6 months previously. It had gradually enlarged, and then, in the last couple of weeks, it became considerably bigger. It was uncomfortable rather than painful and he was now worried about its appearance. Apart from this, he was well and was still at work.
On examination, the lump was soft, smooth, not tender and definitely fluctuated, although it did not transilluminate. At the centre of the mass, the overlying skin was adherent to the lump and, as can be seen, was slightly reddened. However, the skin did not feel warmer than its surrounds.
He was afebrile. There was no other lymphadenopathy, no local focus of infection on full clinical examination, and the spleen and liver could not be felt.
What would be the probable diagnosis ?
