271 Cerebellar Metastasis of Prostatic Ductal Adenocarcinoma, Beyond What We Know

Ductal adenocarcinoma is an uncommon and complex subtype of prostatic adenocarcinoma that demonstrates distinct growth patterns and molecular mutation. Herein, we report a case of metastatic ductal adenocarcinoma in cerebellum, which shows the unique tumoral growth pattern as well as immunoprofile. The patient was a 75-year-old man initially presenting with gait ataxia and headache. A head CT scan revealed a large ill-defined invading cerebellar mass. Microscopically, the mass demonstrated a high-grade macropapillary adenocarcinoma that was diffusely positive for CK7 and TTF-1, and focally positive for PSA, causing the confusion in determining site of origin. The whole body PET scan was subsequently performed for further investigation and revealed a strong signal in the prostate region, along with a lung and multiple osseous lesions. Additional immunostaining, including racemase, PSAP, and androgen receptor. further confirmed a prostate primary. Brain metastasis from ductal carcinoma of prostate is an exceedingly rare occurrence. To the best of our knowledge, this is the first report of prostatic ductal adenocarcinoma initially presenting as a cerebellar metastasis. Reviewing articles show metastatic ductal adenocarcinoma lacks the predilection for metastasis to the meninges as that of typical acinar adenocarcinomas. The distinct biological behavior and aberrant immunohistochemical expressions by ductal adenocarcinoma, especially when it occurs as a metastasis, are oftentimes the diagnostic pitfall. Moreover, the unique cytomorphologic features as well as indolent clinical courses of ductal adenocarcinomas indicate the distinct cytogenetic alteration harbored by this entity.