The vast majority of prostatic neoplasms are epithelial, and the most common is conventional acinar prostatic adenocarcinoma. This chapter will focus exclusively on unusual epithelial and non-epithelial neoplasms that may involve the prostate. The unusual primary epithelial tumors of the prostate that will be discussed in this chapter are: mucinous adenocarcinoma of the prostate; prostatic ductal adenocarcinoma, intraductal carcinoma of the prostate, and squamous cell carcinoma; sarcomatoid carcinoma of the prostate; prostatic carcinoid tumor; prostatic adenocarcinoma with paneth cell-like neuroendocrine differentiation; small cell carcinoma; basal cell carcinoma; urothelial carcinoma; and mucin-producing urothelial-type adenocarcinoma (prostatic urethral adenocarcinoma). The unusual secondary epithelial tumors of the prostate that will be discussed in this chapter include: urothelial carcinoma and colorectal adenocarcinoma. The unusual primary mesenchymal tumors of the prostate included in this chapter include: stromal tumor of unknown malignant potential and stromal sarcoma. Gastrointestinal stromal tumor arising from the colorectal wall is the unusual secondary mesenchymal tumor of the prostate that will be discussed in this chapter.