RESUMEN
BACKGROUND: Prostate adenocarcinoma is the most frequent cancer type among men, followed by skin cancer. Patients with prostate cancer usually present lower urinary tract symptoms due to tumor involvement. Bone marrow invasion is associated with prostate cancer metastasis and is common if blastic lesions in bones are present but is very rare without a large bone involvement and uncommon as initial presentation. CASE PRESENTATION: We present a case of an 86-year-old Caucasian man with bone marrow invasion of prostate cancer without urological or bone-related symptoms and without prostate nodules. His findings were dyspnea, fatigue, and tachycardia. We detail the complete investigation of the case until we found the accurate diagnosis. The patient started treatment, but he had no response and so the oncology team started palliative care. CONCLUSION: Bone marrow invasion as an initial manifestation of prostate cancer is not common, especially if no prostatic lesions are found. This report is important to provide additional information about prostate cancer management.