Positron emission tomography-computed tomography can be useful in the early detection of metastases in primary mucinous carcinoma of the skin on the head and neck.

Primary mucinous carcinoma of the skin (PMCS) is a rare cutaneous malignant neoplasm; its regional node metastasis is also rare. Currently, positron emission tomography-computed tomography (PET-CT) is known to be a useful tool to search for early metastatic lesions in various carcinomas. However, PET-CT is not always specific for head and neck lesions because of physiological uptake in the brain, palatine tonsil, salivary gland, thyroid etc. Herein we present two cases of head and neck PMCS in which metastasis was diagnosed accurately by PET-CT. In these cases, nodal uptake of fluorodeoxy-d-glucose (FDG) histopathologically proved PMCS metastasis, verifying the utility of PET-CT in detail. A surgeon was involved in the verification to compare the histopathological manifestations with the imaging results. Histopathologically, two of 13 nodes were positive in case 1, and one of 41 nodes was positive in case 2. These positive nodes were completely in accordance with the FDG uptake findings with no false negative findings. In treating PMCS on head and neck lesions, PET-CT may be useful in the preoperative assessment when planning the extent of resection.