In breast pathology, pseudoangiomatous stromal hyperplasia, commonly abbreviated PASH, is an overgrowth of myofibroblastic cells and has an appearance similar to fibroadenomatoid changes.

The diagnostic significance is currently uncertain, but it appears to be benign. There have been cases of PASH diagnosed where the tumors co-exist with breast cancer. Other cases have made screening for breast cancer difficult and in some cases impossible due to the number and density of the existing PASH tumors. These cases have resulted in the necessity of a mastectomy and double mastectomy.

They are the most common breast tumor in adolescent women. They also occur in a small number of post-menopausal women. Their incidence declines with increasing age, and, in general, they appear before the age of thirty years.

The management of PASH is controversial. Excision may be indicated in enlarging masses or lesions with atypical features.

The treatment of hyperplasia would consist upon "which"; in the case of benign prostate hyperplasia the combination of alpha-1-receptor blockers and 5-alpha-reductase inhibitors are effective.

10-year survival rates for mucinous tumors is excellent in the absence of invasion.

In the case of borderline tumors confined to the ovary and malignant tumors without invasion, the survival rates are 90% or greater. In invasive mucinous cystadenocarcinomas, the survival is approximately 30%

Hemangioblastomas can cause polycythemia due to ectopic production of erythropoietin as a paraneoplastic syndrome.

Prostatic stromal tumour of uncertain malignant potential, abbreviated PSTUMP, is a rare tumour of the prostate gland stroma that may behave benign or like cancer, i.e. "malignant".

It can be abbreviated STUMP; an abbreviation used for a uterine lesion of uncertain malignant potential.

It is also known as prostatic stromal proliferation of uncertain malignant potential (abbreviated PSPUMP).

Fibroadenomas, are benign breast tumours characterized by an admixture of stromal and epithelial tissue. Breasts are made of lobules (milk producing glands) and ducts (tubes that carry the milk to the nipple). These are surrounded by glandular, fibrous and fatty tissues. Fibroadenomas develop from the lobules. The glandular tissue and ducts grow over the lobule to form a solid lump.

Since both fibroadenomas, and breast lumps as a sign of breast cancer can appear similar, it is recommended to perform ultrasound analyses and possibly tissue sampling with subsequent histopathologic analysis in order to make a proper diagnosis. Unlike typical lumps from breast cancer, fibroadenomas are easy to move, with clearly defined edges.

Fibroadenomas are sometimes called breast mice or a breast mouse owing to their high mobility in the breast.

Atypical hyperplasia is a high-risk premalignant lesion of the breast. It is believed that atypical ductal hyperplasia (ADH) is a direct precursor for low-grade mammary ductal carcinoma, whereas atypical lobular hyperplasia (ALH) serves as a risk indicator.

Some of the more commonly known clinical forms of hyperplasia, or conditions leading to hyperplasia, are:

- Benign prostatic hyperplasia, also known as prostate enlargement.

- Cushing's disease – Physiopathology of hyperplasia of adrenal cortex due to increased circulating level of ACTH (adrenocorticotropic hormone).

- Congenital adrenal hyperplasia – Inherited disorder of gland (adrenal).

- Endometrial hyperplasia – Hyperproliferation of the endometrium, usually in response to unopposed estrogen stimulation in the setting of polycystic ovary syndrome or exogenous administration of hormones. Atypical endometrial hyperplasia may represent an early neoplastic process which can lead to endometrial adenocarcinoma. The development of endometrial adenocarcinoma from endometrial hyperplasia is a typical example of how the effects of pathologic hyperplasia can lead to neoplasia, and females who exhibit hyperplasia of the endometrium are indeed more likely to develop cancer of these cells.

- Hemihyperplasia when only half (or one side) of the body is affected, sometimes generating limbs of different lengths.

- Hyperplasia of the breast – "Hyperplastic" lesions of the breast include "usual ductal hyperplasia", a focal expansion of the number of cells in a terminal breast duct, and "atypical ductal hyperplasia", in which a more abnormal pattern of growth is seen, and which is associated with an increased risk of developing breast cancer.

- Intimal hyperplasia – The thickening of the tunica intima of a blood vessel as a complication of a reconstruction procedure or endarterectomy. Intimal hyperplasia is the universal response of a vessel to injury and is an important reason of late bypass graft failure, particularly in vein and synthetic vascular grafts.

- Focal epithelial hyperplasia (also known as Heck's disease) – This is a wart-like growth in the mucous tissues of the mouth or, rarely, throat that is caused by certain sub-types of the human papillomavirus (HPV). Heck's disease has not been known to cause cancer.

- Sebaceous hyperplasia – In this condition, small yellowish growths develop on the skin, usually on the face. This condition is neither contagious nor dangerous.

- Compensatory liver hyperplasia – The liver undergoes cellular division after acute injury, resulting in new cells that restore liver function back to baseline. Approximately 75% of the liver can be acutely damaged or resected with seemingly full regeneration through hepatocyte division, i.e., hyperplasia. This is what makes living-donor liver transplants possible.

Uterine sarcoma are rare, out of all malignancies of the uterine body only about 4% will be uterine sarcomas. Generally, the cause of the lesion is not known, however patients with a history of pelvic radiation are at higher risk. Most tumors occur after menopause.

Women who take long-term tamoxifen are at higher risk.

Atypical hyperplasia is a benign (noncancerous) cellular hyperplasia in which cells show some atypia. In this condition, cells look abnormal under a microscope and are increased in number.

A stromal tumor is a tumor that arises in the supporting connective tissue of an organ.

Endometrial hyperplasia is a condition of excessive proliferation of the cells of the endometrium, or inner lining of the uterus.

Most cases of endometrial hyperplasia result from high levels of estrogens, combined with insufficient levels of the progesterone-like hormones which ordinarily counteract estrogen's proliferative effects on this tissue. This may occur in a number of settings, including obesity, polycystic ovary syndrome, estrogen producing tumours (e.g. granulosa cell tumour) and certain formulations of estrogen replacement therapy. Endometrial hyperplasia is a significant risk factor for the development or even co-existence of endometrial cancer, so careful monitoring and treatment of women with this disorder is essential.

Endometrial stromal tumors are a group of stromal tumors of the uterus of low to high-grade of malignity.

Phyllodes tumors are considered to be on a spectrum of disease that consists of fibroadenoma, fibroadenoma variant and benign phyllodes. Some would extend the spectrum to include malignant phyllodes tumors and frank sarcoma.

Hemangioblastoma are among the rarest central nervous system tumors, accounting for less than 2%. Hemangioblastomas usually occur in adults, yet tumors may appear in VHL syndrome at much younger ages. Men and women are approximately at the same risk. Although they can occur in any section of the central nervous system, they usually occur in either side of the cerebellum, the brain stem or the spinal cord.

Fibroepithelial neoplasms (or tumors) are biphasic tumors. This means they consist of epithelial tissue, and stromal or mesenchymal tissue. They may be benign or malignant.

Examples include:

- Brenner tumor of the Ovary

- Fibroadenoma of the Breast

- Phyllodes tumor of the Breast

Some therapies for other forms of cancer increase the lifetime risk of endometrial cancer, which is a baseline 2–3%. Tamoxifen, a drug used to treat estrogen-positive breast cancers, has been associated with endometrial cancer in approximately 0.1% of users, particularly older women, but the benefits for survival from tamoxifen generally outweigh the risk of endometrial cancer. A one to two-year course of tamoxifen approximately doubles the risk of endometrial cancer, and a five-year course of therapy quadruples that risk. Raloxifene, a similar drug, did not raise the risk of endometrial cancer. Previously having ovarian cancer is a risk factor for endometrial cancer, as is having had previous radiotherapy to the pelvis. Specifically, ovarian granulosa cell tumors and thecomas are tumors associated with endometrial cancer.

Low immune function has also been implicated in endometrial cancer. High blood pressure is also a risk factor, but this may be because of its association with obesity. Sitting regularly for prolonged periods is associated with higher mortality from endometrial cancer. The risk is not negated by regular exercise, though it is lowered.

A cystic nephroma, also known as multilocular cystic nephroma, mixed epithelial stromal tumour (MEST) and renal epithelial stromal tumour (REST), is a type of rare benign kidney tumour.

Thecomas or theca cell tumors are benign ovarian neoplasms composed only of theca cells. Histogenetically they are classified as sex cord-stromal tumours.

They are typically estrogen-producing and they occur in older women (mean age 59; 84% after menopause). (They can, however, appear before menopause.)

60% of patients present with abnormal uterine bleeding, and 20% have endometrial carcinoma.

In medicine, desmoplasia is the growth of fibrous or connective tissue. It is also called desmoplastic reaction to emphasize that it is secondary to an insult. Desmoplasia may occur around a neoplasm, causing dense fibrosis around the tumor, or scar tissue (adhesions) within the abdomen after abdominal surgery.

Desmoplasia is usually only associated with malignant neoplasms, which can evoke a fibrosis response by invading healthy tissue. Invasive ductal carcinomas of the breast often have a scirrhous, stellate appearance caused by desmoplastic formations.

Endometrial stromal sarcoma is a malignant subtype of endometrial stromal tumor arising from the stroma (connective tissue) of the endometrium rather than the glands. There are three grades for endometrial stromal tumors, as follows. It was previously known as "endolymphatic stromal myosis" because of diffuse infiltration of myometrial tissue or the invasion of lymphatic channels.

Smoking and the use of progestin are both protective against endometrial cancer. Smoking provides protection by altering the metabolism of estrogen and promoting weight loss and early menopause. This protective effect lasts long after smoking is stopped. Progestin is present in the combined oral contraceptive pill and the hormonal intrauterine device (IUD). Combined oral contraceptives reduce risk more the longer they are taken: by 56% after four years, 67% after eight years, and 72% after twelve years. This risk reduction continues for at least fifteen years after contraceptive use has been stopped. Obese women may need higher doses of progestin to be protected. Having had more than five infants (grand multiparity) is also a protective factor, and having at least one child reduces the risk by 35%. Breastfeeding for more than 18 months reduces risk by 23%. Increased physical activity reduces an individual's risk by 38–46%. There is preliminary evidence that consumption of soy is protective.

Fertility subsequent to treatment of surface epithelial-stromal tumors depends mainly on histology and initial

staging to separate it into early borderline (or more benign) versus advanced stages of borderline (or more malignant). Conservative management (without bilateral oophorectomy) of early stage borderline tumors have been estimated to result in chance of over 50% of spontaneous pregnancy with a low risk of lethal recurrence of the tumor (0.5%). On the other hand, in cases of conservative treatment in advanced stage borderline tumors, spontaneous pregnancy rates have been estimated to be 35% and the risk of lethal recurrence 2%.