A prostate cancer pathology report often contains unfamiliar medical terms, including “perineural invasion,” or PNI. This finding on a biopsy or surgical specimen can raise questions about its significance for a prostate cancer diagnosis. This article clarifies what perineural invasion means in prostate cancer, how pathologists identify it, and its implications for understanding the disease.
Defining Perineural Invasion
Perineural invasion (PNI) describes a specific characteristic where cancer cells interact with nerve fibers. The term “peri” means around, and “neural” refers to nerves, indicating that cancer cells are found growing along or surrounding these delicate nerve structures within the prostate gland. These nerves can act as tiny pathways for cancer cells to move through the tissue.
Pathologists identify PNI by carefully examining prostate tissue under a microscope. This examination occurs after a biopsy, where small tissue samples are taken, or following a radical prostatectomy, which involves the surgical removal of the prostate gland. The presence of cancer cells physically associated with nerve bundles is then noted in the pathology report.
Prognostic Significance of Perineural Invasion
The presence of perineural invasion (PNI) in a prostate cancer pathology report is generally considered an adverse prognostic factor. This means it is associated with a more aggressive form of the disease. While not the sole determinant of a cancer’s behavior, PNI contributes to the overall picture of the tumor’s potential for spread.
PNI is often linked to other indicators of more advanced disease. It frequently correlates with a higher risk of extracapsular extension (ECE), where cancer cells have grown beyond the prostate’s outer boundary. PNI also shows an association with seminal vesicle invasion (SVI), where cancer has spread into the seminal vesicles, glands adjacent to the prostate.
PNI is commonly found in tumors with higher Gleason scores. The Gleason score is a grading system reflecting how abnormal cancer cells look under a microscope, with higher scores indicating more aggressive cell patterns. While PNI itself does not increase the Gleason score, its co-occurrence suggests a tumor with a greater tendency for local progression.
Influence on Treatment Decisions
The identification of perineural invasion (PNI) can influence the approach to prostate cancer treatment. This finding helps medical teams determine whether active surveillance remains an appropriate choice or if a definitive treatment, such as surgery or radiation, is more advisable. While PNI alone may not always be a contraindication for active surveillance, it can indicate a higher risk of disease progression.
For patients undergoing radical prostatectomy, the surgical removal of the prostate, PNI can guide the surgeon’s technique. If PNI is identified, particularly on one side, the surgeon might consider a wider excision of tissue in that area. This approach aims to ensure complete removal of the cancer, though it could potentially affect nerve-sparing procedures designed to preserve erectile function. Some studies suggest that bilateral nerve-sparing might still be feasible for select men with PNI without compromising oncological outcomes.
When radiation therapy is chosen, the presence of PNI might influence the treatment plan. This could lead to a larger radiation field to encompass areas of potential microscopic spread. It could also prompt the addition of hormone therapy, which can make radiation more effective by shrinking the prostate and making cancer cells more susceptible to radiation.
Association with Cancer Recurrence
Beyond initial diagnosis and treatment planning, perineural invasion (PNI) is also considered when evaluating the long-term outlook after prostate cancer treatment. The concern shifts to the possibility of cancer returning, often detected through a rising PSA level, known as biochemical recurrence. This rise in prostate-specific antigen (PSA) in the blood after treatment suggests the presence of residual or recurring cancer cells.
Studies have explored the connection between PNI and the likelihood of biochemical recurrence following both radical prostatectomy and radiation therapy. Research indicates that PNI is a risk factor for a higher chance of recurrence.
PNI is one of several factors used to estimate recurrence risk. Other significant indicators include the Gleason score, the pathological stage of the cancer, and the status of surgical margins. The presence of PNI suggests an elevated risk, but it does not guarantee that the cancer will return. All these elements are considered collectively to provide a comprehensive assessment of a patient’s long-term prognosis.