Prostate cancer - causes , symptoms and treatment.

 Prostate cancer, usually refers to prostate adenocarcinoma, where adeno- means gland and carcinoma refers to uncontrolled growth of cells - so prostate cancer is a tumor or growth that originates in the prostate gland.

 Only males are born with a prostate, so this condition only affects males and not females. Typically, when there’s a prostate cancer it’s considered malignant, meaning that the tumor cells can metastasize, or invade and destroy surrounding tissues as well as tissues throughout the body. The prostate is a small gland, about the size and shape of a walnut, that sits under the bladder and in front of the rectum. The urethra which is the tube through which urine leaves the bladder, goes through the prostate before reaching the penis. And that part of the urethra is called the prostatic urethra. The prostate is covered by a capsule of tough connective tissue and smooth muscle. Beneath this layer, the prostate can be divided into a few zones. The peripheral zone, which is the outer most posterior section, is the largest of the zone and contain about 70% of the prostate’s glandular tissue. Moving inward, the next section is the central zone which contains about 25% of the glandular tissue as well as the ejaculatory ducts that join with the prostatic urethra. Last, is the transitional zone, which contains around 5% of the glandular tissue as well as a portion of the prostatic urethra.

 The transitional zone gets its name because it contains transitional cells which are also found in the bladder. The transitional zone undergoes hyperplasia,or an increase in the number of cells, in a large percentage of older men, and that often leads to compression of the urethra. This is called benign prostatic hyperplasia and is often considered a normal part of aging. 

At the microscopic level, each of the tiny glands that make up the prostate is surrounded by a basement membrane made largely of collagen. Sitting within that basement membrane, is a ring of cube-shaped basal cells as well as a few neuro endocrine cells interspersed throughout. Finally, there’s an inner ring of luminal columnar cells, which are within the lumen or center of the gland. Luminal cells secrete substances into the prostatic fluid, that make it slightly alkaline that give it nutrients which nourish the sperm and help it survive in the acidic environment of the vagina. During an ejaculation, sperm leave the testes,travel through the vas deferens, into the ejaculatory ducts, and travel through the prostatic urethra. Smooth muscles in the prostate contract and push the prostatic fluid into the urethra where it joins the sperm as well as the semen which is the fluid that comes from the seminal vesicles.

 The luminal cells also produce prostate specific antigen, or PSA, which helps to liquefy the gel-like semen after ejaculation, there by freeing the sperm to swim. The basal cells and luminal cells of the prostate rely on stimulation from androgens, or male sex hormones, for survival. The androgens include testosterone, which is produced by the testicles, androstenedione and dehydro epiandrosterone which are produced by the adrenal glands, and dihydro testosterone, which is made from testosterone by the prostate itself. Without these androgens, the normal prostate cells, particularly the luminal cells, cannot survive, and undergo apoptosis or programmed cell death. For example, if the testicles are castrated,or removed for some reason, the prostate significantly shrinks in size, largely due to death of the luminal cells.

 Prostate adenocarcinoma most often results from a genetic mutation in a luminal cell, but can also be a basal cell, and it results in that cell dividing uncontrollably. Some risk factors for a genetic mutation include old age, obesity, and a high fat-low fiber diet. Mutations in two genes that have been linked specifically to prostate cancer are breast cancer gene 1 and breast cancer gene 2, also known as BRCA 1 and BRCA 2 - both of which also cause breast cancer. Once a cancer-causing mutation occurs with in a cell, the affected cell begins to grow and replicate out of control, forming a tumor. Early on, prostate cancer cells depend heavily on androgens for survival, but eventually, the cancer cells mutate and find a way to keep multiplying without relying on androgens.

 Overall, prostate cancer cells have a relatively slow rate of growth compared to other types of cancers. Finally, even though prostate adenocarcinoma is the most common type of prostate cancer, other rare types exist as well. These typically arise from other cell types in the prostate, for example transitional cell carcinoma arises from cells in the transitional zone, and small cell prostate cancer arises from neuroendocrine cells. 

Early on, prostate cancer typically causes no symptoms. That’s because the majority of prostate cancers arise in the posterior peripheral zone, which is far away from the urethra. As a result, these tumors can grow quite large before they cause problems with urination. Over time, if the cancer does compress or invade the urethra or bladder, it can cause difficulty urinating, bleeding, and pain with urination and ejaculation. If the cancer becomes metastatic, it most commonly spreads to the bones, like the vertebrae or pelvis, resulting in hip or lower back pain. Prostate cancer can be detected by a digital rectal examination, which is where a finger, is inserted into the rectum to feel against the anterior wall of the rectum which lies along the posterior part of the prostate. A tumor located here would feel like an irregularly hard lump. But if the tumor arises elsewhere, like in the anterior peripheral zone, then the tumor would be out of reach during the digital rectal exam.

 Another approach is to use a trans rectal ultrasound or MRI to image the prostate. Prostate cancer can also cause an elevation in the prostate specific antigen. But ultimately, the diagnosis of prostate cancer requires a biopsy, so that the cells can be scored using the Gleason grading system. The Gleason scale identifies the two most common cell patterns within the prostate tissue and assigns a score between one and five to both of them. A score of 1 represents normal, well differentiated cells, and a score of 5 represents highly abnormal cells that barely resemble the normal prostate tissue. Once the primary and secondary patterns have each received a score from one to five, these two numbers are added together, resulting in a total Gleason score between two and 10 with two representing low-grade tumors and 10 representing high-grade, dangerous tumors.

 In terms of treatment,

 when the tumor is confined to the prostate, and hasn’t metastasized, active surveillance is usually done. This includes routine tumor marker measurement as well as imaging, to ensure that the prostate cancer remains confined to the prostate. If the tumor spreads beyond that point, treatment options include surgery, radiation therapy, chemotherapy, and hormonal therapy.

 Alright, as a quick recap… 

prostate cancer usually refers to prostate adenocarcinoma, but can also include more rare types of tumors as well. It typically begins in the posterior peripheral zone of the prostate and can be detected using a digital rectal examination. Typically, a serum prostate specific antigen is also elevated in prostate cancer. Treatment may include chemotherapy, radiation therapy, surgery, and hormonal therapy, but active surveillance is also an option in many cases where it’s localized  to  the prostate.