Fig. 3.

Metastatic HPV-related NK SCC versus a benign branchial cleft cyst. On low power, a cystic metastasis consists of a simple intranodal cyst with a slightly thickened lining (a). On higher power, a lack of maturation towards the surface and nuclear atypia are helpful features to diagnose NK SCC (b). Within the center of the cystic metastasis are numerous maturing and degenerating squamous cells that may mimic K SCC and be p16 negative on FNA. Branchial cleft cysts, like cystic metastases, have a squamous lining and are surrounded by lymphoid tissue that in some cases is a lymph node. The squamous lining may show reactive atypia, (c) but still matures towards the surface