There are more than a dozen recognized types of prostate cancer, but one type dominates: acinar adenocarcinoma accounts for 90 to 95 percent of all diagnoses. The remaining 5 to 10 percent is split among several rare forms, each with distinct behavior, detection challenges, and treatment considerations. Understanding which type is involved matters because not all prostate cancers grow the same way or respond to the same therapies.
Acinar Adenocarcinoma: The Common Type
When people refer to “prostate cancer” without further detail, they almost always mean acinar adenocarcinoma. This cancer develops in the small, round glands (acini) that produce prostatic fluid. It typically raises PSA levels in the blood, which is why routine PSA screening catches it effectively. Acinar adenocarcinoma is graded using the Gleason scoring system, where a pathologist examines tissue samples and assigns a score reflecting how abnormal the cells look. Lower scores suggest slower-growing cancer; higher scores indicate more aggressive disease.
Within acinar adenocarcinoma, pathologists recognize several subtypes based on the pattern of cells under the microscope. These include atrophic, foamy gland, and pseudohyperplastic patterns, among others. The World Health Organization now uses the term “subtypes” rather than “variants” for these distinct categories. While the specific subtype can influence how difficult the cancer is to identify on a biopsy, most acinar adenocarcinomas are managed using the same general treatment framework of surveillance, surgery, radiation, or hormone therapy, depending on grade and stage.
Ductal Adenocarcinoma
Ductal adenocarcinoma arises in the cells lining the prostatic ducts rather than the small glands. It can occur in a pure form or mixed with standard acinar adenocarcinoma. In a study of 31 patients, about half had pure ductal tumors while the other half had mixed ductal/acinar disease. Most cases were located within the prostate itself, though a small number originated in the urethra.
This type tends to behave like high-grade acinar adenocarcinoma. Seventy percent of patients in one series had stage T2c or higher disease at the time of diagnosis, meaning the cancer had already grown through a significant portion of the prostate. The median age at diagnosis was 69. Unlike some rare types, ductal adenocarcinoma does produce PSA and does respond to hormone-blocking treatment, with 13 out of 17 patients responding well to androgen deprivation therapy. Good local control is achievable through either surgery or radiation, though the risk of eventual metastasis remains high.
Neuroendocrine Prostate Cancer
Neuroendocrine prostate cancer (NEPC) is one of the most aggressive forms. The WHO groups it into five subcategories: small cell carcinoma (the most well-known), large cell neuroendocrine carcinoma, carcinoid tumors, adenocarcinoma with Paneth cells, and adenocarcinoma with neuroendocrine differentiation.
NEPC can arise on its own or develop when a standard adenocarcinoma transforms after prolonged hormone therapy. This distinction matters clinically. Tumors that start as neuroendocrine cancers tend to have very low PSA levels and don’t rely on testosterone to grow, which means standard hormone-blocking drugs are ineffective. Tumors that transform from adenocarcinoma may still show some PSA elevation. Regardless of origin, the prognosis is poor: the five-year survival rate sits at roughly 14 percent. Because PSA levels often stay low, these cancers can grow undetected by standard screening.
Transitional Cell (Urothelial) Carcinoma
Transitional cell carcinoma, also called urothelial carcinoma of the prostate, originates in the transitional epithelial cells that line the prostatic urethra and periurethral ducts. It represents only 0.4 to 2 percent of all prostate tumors. This type develops at the junction between glandular prostate tissue and the urethral lining, which is why it can arise from either the mucosa covering the prostatic urethra or from the prostatic ducts themselves.
Because this cancer is biologically similar to bladder cancer rather than typical prostate cancer, it is treated more like a bladder malignancy, often with platinum-based chemotherapy. It does not reliably raise PSA levels, which makes it harder to catch early through routine prostate screening. The prognosis is generally worse than for standard adenocarcinoma.
Squamous Cell Carcinoma
Squamous cell carcinoma of the prostate is extremely rare. Unlike adenocarcinoma, it develops from the flat cells found in the prostate rather than glandular tissue. It does not produce PSA, so it won’t show up on a standard PSA blood test. This type does not respond to hormone therapy because its growth isn’t driven by testosterone. Treatment typically involves chemotherapy or radiation rather than the hormone-based approaches used for most prostate cancers.
Sarcomas and Other Rare Types
Several additional rare cancers can originate in the prostate:
- Sarcomas arise from the muscle or connective tissue of the prostate rather than glandular cells. They tend to affect younger men compared to adenocarcinoma and do not raise PSA levels.
- Sarcomatoid carcinoma is a hybrid tumor containing both carcinoma and sarcoma-like elements. It is aggressive and also PSA-silent.
- Adenoid cystic carcinoma (sometimes called basal cell carcinoma of the prostate) develops from the basal cells at the base of the prostatic glands. The WHO prefers the term “adenoid cystic” to avoid confusion with the common skin cancer of the same name.
- Lymphoma of the prostate occurs when cancers of the immune system develop in prostatic tissue. It is managed as a blood cancer rather than a prostate cancer.
Why Type Matters for Detection
One of the most practical things to know about prostate cancer types is that PSA testing, the standard screening tool, works well for acinar and ductal adenocarcinoma but is unreliable for most other types. Neuroendocrine tumors, squamous cell carcinoma, sarcomas, sarcomatoid carcinoma, adenoid cystic carcinoma, and lymphoma are all less likely to raise PSA levels. This means a normal PSA result doesn’t guarantee the absence of prostate cancer, particularly the aggressive rare forms.
Pathologists also now recognize a precancerous condition called intraductal carcinoma of the prostate (IDC-P), which may represent two distinct situations. A small subset develops from a precursor lesion and is truly “in situ,” meaning it hasn’t spread beyond its original location. The majority, however, appear as a late event linked to high-grade invasive cancer that has already colonized normal prostatic ducts. Finding IDC-P on a biopsy typically signals that aggressive cancer is present or nearby.
For the vast majority of men diagnosed with prostate cancer, the type will be acinar adenocarcinoma, and the Gleason grade and stage will drive treatment decisions. But when a tumor turns out to be one of the rarer types, identifying it correctly is critical because the treatment approach, expected behavior, and prognosis can be fundamentally different.