Cancer of unknown primary eventually diagnosed as poorly differentiated prostate cancer: a case report

BACKGROUND: Prostate cancer has been well known to have a high prevalence among middle-aged and older men, with high incidence of metastases to the bone—the main metastatic site. However, prostate cancer among those less than 50 years of age is extremely rare, and neck swelling is seldom the initial symptom. CASE PRESENTATION: We herein report case of a 47-year-old Japanese male with poorly differentiated prostate cancer that had been initially diagnosed as a cancer of unknown primary with multiple lymph node and bone metastases before reaching a definitive diagnosis. The patient has been started on endocrine therapy and is currently alive without progression. DISCUSSION AND CONCLUSION: When locating the primary lesion in men with cancer of unknown primary, it is important to consider the possibility of prostate cancer, confirm serum prostate-specific antigen levels, and perform local prostate evaluation.