Brain metastasis from prostate small cell carcinoma: not to be neglected.

Background: Symptomatic brain metastases from prostatic carcinoma are rare (0.05% to 0.5%).
Case Report: A 70-year-old man presented with a homonymous hemianopsia due to brain metastatic prostatic carcinoma shortly before becoming symptomatic of prostatic disease. CT and MRI of the brain showed a tumour deep in the right hemisphere near the thalamus and involving the optic radiation.
Results: Routine haematological and biochemical tests were normal. The prostate specific antigen level was low on two separate occasions. The prostatic and brain tumours showed identical appearances, namely of a poorly differentiated adenocarcinoma with neuroendocrine differentiation (small cell carcinoma).
Conclusion: A literature review suggests that small cell carcinoma of the prostate is more likely to spread to the brain compared to adenocarcinoma and that brain metastases indicate a poor prognosis. The prostate gland should be remembered as a possible cause of brain metastases and that a normal serum prostate specific antigen does not exclude this diagnosis.