Types of Prostate Cancer: Common and Rare Forms Explained

Understanding your prostate cancer type is crucial for determining the most effective treatment approach and predicting outcomes. Not all prostate cancers behave the same way, and identifying the specific type helps your medical team create a personalized treatment plan tailored to your unique situation.

When prostate cancer is diagnosed, pathologists examine cancer cells under a microscope to identify their characteristics and behaviors. This examination reveals critical information about the cancer type, which is documented in a detailed pathology report. This report serves as a roadmap for your healthcare team to make informed decisions about your care.

The majority of prostate cancers are classified as carcinomas, which originate in epithelial tissue lining the prostate glands and ducts. However, several distinct types exist, each with unique characteristics, behaviors, and treatment responses. This comprehensive guide explores the various types of prostate cancer to help you better understand your diagnosis and engage in meaningful conversations with your healthcare providers.

Understanding Prostate Cancer Classification

Prostate cancer classification is based on the microscopic appearance of cancer cells and their origin within the prostate tissue. The prostate gland contains different types of cells, and cancer can develop from any of these cell types, leading to various cancer forms with distinct characteristics.

Most prostate malignancies are carcinomas that develop in the epithelial tissue forming the lining of prostate glands and ducts. The specific appearance of these cells, their growth patterns, and their response to laboratory tests determine the exact cancer type. Pathologists use specialized terminology to describe these findings, which may seem complex but provides essential information for treatment planning.

Common Types of Prostate Cancer

Acinar Adenocarcinoma

Acinar adenocarcinoma is by far the most prevalent form of prostate cancer, accounting for more than 95% of all diagnoses. This cancer originates in the acini, which are small, round, pouch-shaped structures within the prostate glands responsible for producing components of seminal fluid.

When cancer cells closely resemble typical acinar adenocarcinoma cells, they are termed “conventional.” However, several subtypes exist when cells display slight variations:

• Pleomorphic Giant Cell Adenocarcinoma: Characterized by unusually large cells with highly variable appearances
• Prostatic Intraepithelial Neoplasia-like Carcinoma (PIN-like): Cancer cells that resemble high-grade prostatic intraepithelial neoplasia (HGPIN), a non-cancerous condition
• Sarcomatoid Carcinoma: Features cells with appearances similar to sarcoma, cancers typically found in bones and connective tissues
• Signet Ring Cell-like Carcinoma: Contains cells resembling signet rings, with distinctive flat-topped appearances

Ductal Adenocarcinoma

Ductal adenocarcinoma is a rare variant that develops in the duct cells of the prostate rather than the acini. These ducts transport fluid from the acini to the urethra, the tube carrying urine and semen out of the body.

Some prostate cancers contain both acinar and ductal cell components. Classification depends on which cell type predominates. When ductal cells are more abundant, the cancer is classified as ductal adenocarcinoma. If acinar cells dominate, it remains classified as acinar adenocarcinoma, though it may be described as having ductal features.

Rare Types of Prostate Cancer

Squamous Cell Carcinoma

Squamous cell carcinoma consists of cells resembling squamous cells, which are thin, flat cells normally found in skin and organ linings. Since squamous cells are not typically present in the prostate, the development mechanism of this rare type remains unclear to researchers.

Adenosquamous Carcinoma

This uncommon type contains a mixture of both adenocarcinoma cells and squamous cell carcinoma cells, combining characteristics of both cancer types.

Adenoid Cystic Carcinoma

Also known as basal cell carcinoma, this rare form originates in the basal cells that provide structural support to the acini and ducts. Under microscopic examination, it closely resembles adenoid cystic carcinoma of the salivary glands, which is how it received its name.

Neuroendocrine Carcinoma

Neuroendocrine carcinoma develops from neuroendocrine cells, which possess characteristics of both nerve cells (signal transmission) and endocrine cells (hormone production). While neuroendocrine carcinomas can occur throughout the body, neuroendocrine prostate cancer (NEPC) is relatively rare at initial diagnosis. It more commonly appears after treatment for prostate adenocarcinoma.

Neuroendocrine prostate cancer includes several subtypes:

• Large Cell Carcinoma: Contains cells that appear large under microscopic examination
• Small Cell Carcinoma: The most common neuroendocrine prostate cancer type, featuring small-appearing cells
• Well-differentiated Neuroendocrine Tumor: Previously called carcinoid tumor, with cells closely resembling healthy cells

Treatment-related neuroendocrine carcinoma of the prostate, also called aggressive variant prostate cancer, can develop when adenocarcinoma transforms into neuroendocrine carcinoma following hormone therapy. This transformation renders the cancer unresponsive to further hormone therapy.

Sarcoma

Sarcomas are cancers originating in bones and connective tissues, typically developing in the arms, legs, or abdomen. Prostate sarcoma is exceptionally rare. Types that can affect the prostate include:

• Leiomyosarcoma: Develops in muscle tissue and is the most common prostate sarcoma in adults
• Rhabdomyosarcoma: Also originates in muscle tissue but primarily affects children
• Prostate Stromal Sarcoma: Develops in prostate connective tissue and occurs exclusively in the prostate, unlike other sarcomas that can develop in multiple body locations

Lymphoma

Lymphoma is a cancer of the lymphatic system, which is part of the immune system. While lymphoma typically affects lymph nodes and other immune system components, it rarely originates in the prostate. Most prostate lymphomas are non-Hodgkin lymphomas, particularly diffuse large B-cell lymphoma and related B-cell lymphomas.

Other Cancers Affecting the Prostate

Some cancers can involve the prostate without being classified as true prostate cancers:

• Urothelial Carcinoma: Originates in cells lining the urinary tract, formerly called transitional cell carcinoma. When found in the prostate, it typically has spread from the bladder or urethra, though it can originate in the portion of the urethra passing through the prostate
• Metastatic Cancer: Cancer that has spread to the prostate from another body location, such as lung, skin, or pancreatic cancer

Determining Cancer Aggressiveness

Cancer aggressiveness refers to how quickly cancer grows and its likelihood of spreading to other body parts. Aggressive cancers typically present greater treatment challenges and may have less favorable outcomes.

Less Aggressive Types

Some prostate cancer types tend to grow more slowly and have lower spreading risks:

• Prostatic intraepithelial neoplasia-like carcinoma
• Well-differentiated neuroendocrine tumor

More Aggressive Types

Several prostate cancer types are typically more aggressive:

• Adenoid cystic carcinoma
• Ductal adenocarcinoma
• Large cell carcinoma
• Pleomorphic giant cell adenocarcinoma
• Prostate lymphoma
• Prostate stromal sarcoma
• Sarcomatoid carcinoma
• Signet ring cell-like adenocarcinoma
• Small cell carcinoma
• Squamous cell carcinoma
• Treatment-related neuroendocrine carcinoma (aggressive variant prostate cancer)

Cancer Grading

Healthcare professionals assess cancer aggressiveness through grading systems. Pathologists compare cancer cells to healthy cells under microscopic examination:

• Low-grade cancers: Cells closely resemble healthy cells, indicating lower aggressiveness
• High-grade cancers: Cells appear significantly different from healthy cells, suggesting higher aggressiveness

While uncommon, prostate cancer can evolve from less aggressive to more aggressive forms. This transformation may become apparent if cancer recurs or spreads (metastasizes). However, for most low-grade adenocarcinomas confined to the prostate, the risk of becoming more aggressive is minimal.

Symptoms Across Different Types

Most prostate cancer types produce similar symptoms, primarily affecting urinary function. Common symptoms include increased urination frequency and difficulty initiating urination.

However, some types may cause additional or distinct symptoms:

• Neuroendocrine Carcinomas: May produce hormones causing weight gain in the torso, prominent stretch marks, and facial rounding
• Sarcoma: Often grows rapidly to considerable size, potentially blocking urine flow or impeding bowel movements
• Lymphoma: May trigger fever, chills, night sweats, and unexplained weight loss

Risk Factors and Causes

The exact causes of most prostate cancers remain unclear to medical researchers. The rarity of many prostate cancer types makes identifying specific causes particularly challenging due to limited research data.

Some types have distinct risk factor patterns:

Age-Related Factors

• Younger Age: Rhabdomyosarcoma predominantly affects children, while prostate lymphoma can occur at any age, including childhood. Prostate stromal sarcoma typically develops in adults under 65
• Older Age: Most types, including acinar adenocarcinoma, are more common in older individuals. Sarcomatoid carcinoma tends to develop at more advanced ages than other types

Treatment-Related Risk Factors

Previous prostate cancer treatments may increase risks for certain types. Hormone therapy and radiation therapy have been associated with elevated risks of squamous cell carcinoma and treatment-related neuroendocrine carcinoma.

Diagnostic Approaches

All prostate cancer types are diagnosed using similar fundamental procedures, including physical examinations, blood tests, imaging studies, and tissue biopsy. The biopsy results provide definitive information about cancer type.

PSA Testing Limitations

The prostate-specific antigen (PSA) test measures PSA protein levels in the blood. Elevated PSA often signals prostate cancer, and this test effectively detects acinar and ductal adenocarcinomas. However, several types are less likely to elevate PSA levels:

• Adenoid cystic carcinoma
• Lymphoma
• Neuroendocrine tumor
• Sarcoma
• Sarcomatoid carcinoma
• Squamous cell carcinoma

Gleason Score Application

The Gleason score is a grading system describing prostate cancer aggressiveness and helping predict cancer behavior. This scoring system applies exclusively to prostate adenocarcinomas and is not used for other prostate cancer types.

Treatment Approaches by Type

When cancer remains confined to the prostate, treatment approaches are often similar across types. Primary options typically include surgical prostate removal (prostatectomy) and radiation therapy, used alone or combined with additional treatments.

Medication-Based Treatments

Treatment differences become more apparent with medication-based therapies, as not all types respond similarly to the same medications. Before starting any medication-based treatment, consult with your healthcare provider to understand which options are most appropriate for your specific cancer type.

• Hormone Therapy: This approach blocks hormones that cancer cells need for survival. However, hormone therapy is ineffective against certain types, including lymphoma, sarcoma, sarcomatoid carcinoma, small cell carcinoma, and squamous cell carcinoma
• Chemotherapy: These medications target rapidly dividing cells. Numerous chemotherapy agents exist, and healthcare professionals consider the specific cell types involved when selecting appropriate medications. For instance, prostate lymphomas receive chemotherapy protocols used for other lymphomas rather than those used for prostate adenocarcinoma

Your doctor will discuss medication options suitable for your specific cancer type and overall health condition. Always consult your healthcare team before starting any treatment to understand potential benefits, risks, and alternatives.

Understanding Your Prognosis

Your prostate cancer type is one of many factors influencing your prognosis and treatment outcomes. Other important considerations include:

• Overall health status and medical history
• Cancer stage and whether it has spread beyond the prostate
• Cancer grade and aggressiveness level
• Age and personal preferences regarding treatment
• Response to initial treatments

Have thorough discussions with your healthcare team about your specific cancer type and what it means for your situation. Ask questions about:

• How your cancer type affects available treatment options
• Expected treatment outcomes and success rates
• Potential side effects and quality of life considerations
• Follow-up care and monitoring requirements
• Resources and support services available to you

Taking the Next Steps

Receiving a prostate cancer diagnosis can feel overwhelming, but understanding your specific cancer type empowers you to make informed decisions about your care. Remember that prostate cancer, particularly adenocarcinoma, often progresses slowly, giving you time to explore options and develop a comprehensive treatment plan with your medical team.

Work closely with specialists experienced in treating your specific cancer type. Consider seeking a second opinion, especially for rare or aggressive forms. Many men benefit from consulting with multidisciplinary teams that include urologists, oncologists, radiation oncologists, and other specialists who can provide comprehensive perspectives on treatment approaches.

Stay informed, ask questions, and actively participate in your healthcare decisions. Your understanding of your prostate cancer type is a valuable tool in your journey toward optimal health outcomes.

Sources:

• National Cancer Institute – Prostate Cancer
• American Cancer Society – Prostate Cancer
• Mayo Clinic – Prostate Cancer
• Urology Care Foundation – Prostate Cancer
• StatPearls – Prostate Cancer