PIN begins to appear in the prostates of some men as early as their 20s. Almost half of all men have PIN by the time they reach 50. High-grade PIN is considered a pre-cancer of the prostate because it may turn into prostate cancer over time. Low-grade PIN in general should not be on a biopsy report, as it has no significance.
The diagnosis of intraductal carcinoma is difficult for pathologists, so you may want to consider asking for a second opinion in this setting.
You should discuss your treatment options with your doctor if your biopsy shows intraductal carcinoma in the absence of usual prostate cancer.
Intraductal carcinoma often represents high-grade prostate cancer that is growing into pre-existing prostate ducts. It is often seen next to high-grade prostate cancer.
In this setting the intraductal carcinoma has no significance and will not change your treatment options or prognosis (outlook).
In this setting, some doctors will recommend treatment, such as surgery or radiation, since intraductal carcinoma is typically associated with high-grade prostate cancer. Other doctors may choose to do a repeat biopsy to try to confirm the high-grade cancer before starting treatment.
- Low-grade PIN: the patterns of prostate cells appear almost normal
- High-grade PIN: the patterns of cells look more abnormal
All of these are terms for things the pathologist might see under the microscope that that are benign (not cancer), but sometimes can look like cancer under the microscope.
Atypical adenomatous hyperplasia (which is sometimes called adenosis) is another benign condition that can sometimes be seen on a prostate biopsy.
Low-grade prostatic intraepithelial neoplasia:
- Nucleoli should be visible with the 20x objective.
- If one uses the 40x objective. one over calls.
- May need IHC for cancer versus HGPIN.
- Nucleoli should be present in >= 10% of cells in a gland to call it HGPIN. 
- This criterium is not required by all pathologists.
- Medium to large glands with architectural changes – see HGPIN architecture below.
- Described as „epithelial hyperplasia“.
- Diagnosed on basis of nuclear changes.
- Hyperchromatic nuclei – key (low power) feature.
- Nucleoli present – key (high power) feature.
- Often increased NC ratio.
- Nuclear enlargement – usually subtle/appreciated at high magnification only.
- Tinctorial changes of the cytoplasm – usually amphophilic (red) or basophilic (blue).
Prostate cancer on follow-up biopsy by number of HGPIN sites from Merrimen et al.: 
on follow-up (95% CI)
- The architectural pattern is not thought to have any prognostic significance; however, it may be useful for differentiating it from benign prostate.
It may be referred to as prostatic intraepithelial neoplasia, abbreviated PIN.
HGPIN – intermed. mag. (WC/Nephron)
HGPIN – high mag. (WC/Nephron)