DIAGNOSIS: Solitary pineal metastasis of prostate adenocarcinoma with changes of secondary acute hydrocephalus
The pineal gland is one of the rarest sites in the brain to find metastatic neoplasms; moreover, prostate adenocarcinoma rarely metastasizes to the central nervous system (1, 3). In a review of the literature, we identified only one other case of metastatic prostate carcinoma where the sole intracranial metastasis was to the pineal gland (2). Indeed, in another study of over 5000 cases of intracranial metastasis only 0.3% involved the pineal gland(5). These most frequently originated from primary carcinomas of the lung, breast, skin (melanoma), or kidney; 50% of these were solitary metastasis within the central nervous system and none were metastatic prostate carcinoma.
The relative infrequency of any metastases to the pineal gland is likely due in part to its small size. It is less clear why metastasis to the pineal gland are so often solitary within the central nervous system. One explanation is that access by tumor to the pineal gland is easier since the pineal lies outside of the blood-brain barrier. Although up to 25% of patients with a malignant neoplasm eventually develop brain metastases, central nervous system involvement by prostate carcinoma is distinctly rare (6). Autopsy studies have reported that only 1-4% of patients with widely metastatic prostate carcinoma have intracranial involvement despite typically widespread bone metastases in virtually all patients who die of prostate carcinoma (5). The metastases of prostate carcinomas are quite heterogeneous with varied immunophenotypes (4). Further molecular profiling may stratify the potential of these malignancies to preferentially metastasize to one organ over another.
Contributed by Bonnie Cole, Thomas J. Montine, Lawrence True, Joshua Sonnen