structural:scholar_edition, information:extraction, quality:correction, linguistic:translation
Diagnosis

Men suspected of having prostate cancer may undergo several tests to assess the prostate. One common procedure is the digital rectal examination, in which a doctor inserts a lubricated finger into the rectum to feel the nearby prostate. Tumors feel like stiff, irregularly shaped lumps against the rest of the prostate. Hardening of the prostate can also be due to benign prostatic hyperplasia; around 20–25% of those with abnormal findings on their rectal exams have prostate cancer. Several urological societies' guidelines recommend magnetic resonance imaging (MRI) to evaluate the prostate for potential tumors in men with high PSA levels. MRI results can help distinguish those who have potentially dangerous tumors from those who do not.

A definitive diagnosis of prostate cancer requires a biopsy of the prostate. Prostate biopsies are typically taken by a needle passing through the rectum or perineum, guided by transrectal ultrasonography, MRI, or a combination of the two. Ten to twelve samples are taken from several regions of the prostate to improve the chances of finding any tumors. Biopsies are sent for a histopathologic diagnosis of prostate cancer, wherein they are examined under a microscope by a pathologist, who determines the type and extent of cancerous cells present. Cancers are first classified based on their appearance under a microscope. Over 95% of prostate cancers are classified as adenocarcinomas (resembling gland tissue), with the rest largely squamous-cell carcinoma (resembling squamous cells, a type of epithelial cell) and transitional cell carcinoma (resembling transitional cells).

Next, tumor samples are graded based on how much the tumor tissue differs from normal prostate tissue; the more different the tumor appears, the faster the tumor is likely to grow. The Gleason grading system is commonly used, where the pathologist assigns numbers ranging from 3 (most similar to healthy prostate tissue) to 5 (least similar) to different regions of the biopsied tissue. They then calculate a "Gleason score" by adding the two numbers that represent the largest areas of the biopsy sample. The lowest possible Gleason score of 6 represents a biopsy most similar to healthy prostate; the highest Gleason score of 10 represents the most severely cancerous. Gleason scores are commonly grouped into "Gleason grade groups", which predict disease prognosis: a Gleason score of 6 is Gleason grade group 1 (best prognosis). A score of 7 (with Gleason scores 4 + 3, or Gleason scores 3 + 4, with the most prominent listed first) can be grade group 2 or 3; it is grade group 2 if the less severe Gleason score (3) covered more area; grade group 3 if the more severe Gleason score (4) covered more area. A score of 8 is grade group 4. A score of 9 or 10 is grade group 5 (worst prognosis).

The extent of cancer spread is assessed by MRI or PSMA scan – a positron emission tomography (PET) imaging technique where a radioactive label that binds the prostate protein prostate-specific membrane antigen is used to detect metastases distant from the prostate. CT scans may also be used, but are less able to detect spread outside the prostate than MRI. Bone scintigraphy is used to test for spread of cancer to bones.