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Cytological findings of metastatic poorly differentiated prostate adenocarcinoma to Virchow's node with immunohistochemical positivity for CD10 and negativity for PSA

Metastatic prostate adenocarcinoma (PAC) to the left supraclavicular lymph node is extremely rare. We report a case of metastasis of PAC to the left supraclavicular lymph node (known as Virchow's node), focusing on both cytological and immunohistochemical findings. The patient was a 72-year-old Japanese man who was referred to our hospital after initially noticing a lump in the left supraclavicular lymph node 3 months previously. CT revealed multiple swollen lymph nodes in the left supraclavicular fossa, left axilla, abdominal aorta and the bilateral internal and external iliac arteries, but the primary site was not identified. Fine-needle aspiration cytology was performed, revealing a large sheet of cohesive tumor cells with indistinct cell borders, a high nuclear/cytoplasmic ratio, granular cytoplasm, eccentric oval to round nuclei, and enlarged prominent nucleoli. Immunohistochemical examination of cell block sections revealed that the tumor cells were positive for CK AE1/AE3 and CD10 and negative for PSA. Since additional immunohistochemistry revealed that tumor cells were diffusely positive for both NKX3.1 and PSMA, the cytological diagnosis was suspected metastatic PAC. PET CT and MRI suggested the high probability of PAC. Prostate core biopsy was performed and a histological diagnosis of poorly differentiated PAC was made (Gleason score 9 = 5 + 4). The patient started therapy for PAC and the tumors were observed to have shrunk at the 1-year follow-up evaluation. Familiarity with and recognition of the characteristic cytopathological findings of metastasis of PAC to Virchow's node are important for making a correct diagnosis.