Metastatic prostate adenocarcinoma to cervical lymph nodes: an unusual diagnosis on fine-needle aspiration biopsy

Introduction: Metastatic prostatic adenocarcinoma (PAC) has mostly involved the pelvic lymph nodes; metastases to the cervical lymph nodes are exceedingly rare.

Materials and methods: A retrospective review of cytopathology files (January 1990 to March 2019) identified 13 cases of metastatic PAC to cervical lymph nodes diagnosed using fine-needle aspiration biopsy (FNAB). The clinical and demographic information were collected from the electronic medical records, and the slides were reviewed.

Results: A total of 13 male patients with a mean age at FNAB 69 years (range, 61-86 years); 12 patients had a known history of PAC. In the patient without a history of PAC, the FNAB finding had been misinterpreted as papillary thyroid carcinoma. The interval between the original diagnosis and cervical lymph node metastasis was 98.5 months (range, 1-288 months). Most involved the left side (85%). Most smears had a clean background with few lymphocytes (46%) and numerous cellular clusters in flat sheets and acini (62%) and were composed of polygonal cells (46%) with round-oval shaped nuclei and indistinct cell borders (92%). The cytoplasm was granular (61%) or scanty (46%). The nuclei were uniform, size ≥2 times that of a neutrophil (69%). Prominent nucleoli and anisonucleosis were seen in 54% of cases; cellular pleomorphism was infrequent (30%). Immunostains confirmed the prostate origin in 7 tissue cores.

Conclusions: Metastatic PAC to the cervical lymph nodes occurs infrequently. If the history is unknown, cases can be misdiagnosed as metastases from cervical neoplasms. The findings indicating metastatic PAC to the cervical lymph nodes on FNAB include involvement of left-sided cervical lymph nodes in elderly male patients and cellular smears composed of uniform polygonal cells, arranged in flat sheets and acini, with granular cytoplasm, indistinct cell borders, and round-oval nuclei with prominent nucleoli.