Prostate processing and embeddingMedical editor A. Kathrine Lie MD
Oslo University Hospital
Typing, grading, and specification of a tumor is a tedious process that is crucial for the choice of treatment method and the prognosis of the patient. The diagnosis is most often made on biopsies from the prostate, but can also be made by coincidence during a transurethral resection of the prostate (TUR-P) performed for therapeutic purposes on patients with incontinence problems.
Pathologists play a key role in diagnosing prostate cancer, since they classify and grade the tumor, determine the extent, and whether there is infiltration of pericapsular tissue, vessels or seminal vesicals. It must also be investigated whether the capsule is intact and if there is tumor present in the resection margins. This is of significant value for the follow-up schedule with PSA testing, and for assessing if the patient will need additional treatment. A positive correlation between MRI findings and macroscopic and microscopic findings is usually present only with large tumors .
The primary cancer diagnosis must always be verified by at least two pathologists.
The criteria used by pathologists to determine malignancy are:
- architectual atypia (invasive growth, perineural infiltration micro and cribriform glands)
- cellular atypia (enlarged nuclei with prominent nucleoli) .
Small foci with carcinoma must be confirmed with with immunohistochemical techniques. When there the tumor grows invasively, there is loss of basal cells and the basal cell markers, 34BE12 and p63 , are lost. The marker, alpha-methylacyl-CoA racemace (AMACR/p504s), is upregulated in prostate carcinoma , and can be detected with immunohistochemical techniques.
The entire prostate gland with seminal vesicles is embedded and examined under a microscope.
Around 40-50 sections are assessed by a pathologist , including large sections from main parts of the prostate .
- The pathologist weighs, measures, describes the external appearance.
- A probe is placed through the urethra to better orient the prostate.
- The surface of the prostate is then dyed. The dorsal surface is dyed black, the left lobe blue, and right lobe green.
- The probe is then removed and the prostate is dried. The seminal vesicals are then cut from the prostate.
- A small end from the apax and base are then cut, and the apex and base are separated through the urethra.
- A sagittal section is made from each half in the apex and base. A cross section is then made of the middle part as a large section.
- A cross section from the seminal vesicals is then made.
- Calcificationsare removed if necessary before the sections are placed in blocks with the referral number and block number.
- All of the sections are fixed for an additional 48 hours in formalin before further processing.
- The blocks are then placed in a processing machine where the tissue is dehydrated, rinsed, and infiltrated with paraffin using alcohol, xylenes, and paraffin.
- The tissue is then embedded in liquid paraffin that solidifies into a block allowing to make very thin slices of tissue.
- The paraffin blocks are stored in a freezer until the sections are made.
- The technician slices 1-2 μmm sections which are transferred to a slide glass in a water bath.
- The sections are then transferred to a staining maching where the paraffin is removed and they are stained with haematoxylin and eosin, dehydrated, and mounted.
It may be necessary to do immunohistochemical testing before the final diagnosis is made.
The result is usually available after one week unless additional analyses are necessary. Complicated cases may require more time. Occasionally, the pathologist will consult an expert out of the country.