APAs are characterized by glands with abnormal shapes that: (1) often have squamous metaplasia, and (2) are surrounded by benign smooth muscle. Nuclear atypia, if present, is mild.

The microscopic differential diagnosis includes endometrial carcinoma and endocervical adenocarcinoma.

Atypical polypoid adenomyoma, abbreviated APA, is a rare uncommon benign tumour of the uterus.

Pain is the most common symptom, followed by either sensorineural or conductive hearing loss, tinnitus or drainage (discharge). A mass lesion may be present, but it is often slow growing.

It is important to correctly identify, as it can be confused with atypical ductal hyperplasia, cribriform ductal carcinoma in situ (DCIS), and adenoid cystic carcinoma.

In obstetrics and gynecology contexts, it is a form of adenomyosis that forms a mass or growth around the tissue of the inner uterus.

Most cases of adenomyosis are non-symptomatic. However, it may present with dysmenorrhea and pelvic pain. In the case of juvenile cystic adenomyoma, laparoscopic enucleation results in a statistically and clinically significant reduction in dysmenorrhea, ease in any chronic pelvic pain, and low risk of recurrence.

Most polyps do not cause noticeable symptoms. Gallbladder polyps are usually found incidentally when examining the abdomen by ultrasound for other conditions, usually abdominal pain.

This tumor only affects the outer 1/3 to 1/2 of the external auditory canal as a primary site. If this area is not involved, the diagnosis should be questioned. The most common tumor type is ceruminous adenoid cystic carcinoma and ceruminous adenocarcinoma, NOS.

Collagenous spherulosis, also mucinous spherulosis and simply spherulosis, is a benign finding in breast pathology. It is almost always an incidental finding, though it is occasionally associated with calcifications, which may lead to a biopsy.

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.

On a subsequent biopsy, given the diagnosis of ASAP, the chance of finding prostate adenocarcinoma is approximately 40%; this is higher than if there is high-grade prostatic intraepithelial neoplasia (HGPIN).

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.

Gallbladder polyps are growths or lesions resembling growths (polypoid lesions) in the wall of the gallbladder. True polyps are abnormal accumulations of mucous membrane tissue that would normally be shed by the body. The main types of polypoid growths of the gallbladder include cholesterol polyp/cholesterosis, cholesterosis with fibrous dysplasia of gallbladder, adenomyomatosis, hyperplastic cholecystosis, and adenocarcinoma.

Adenomyoma is a tumor ("-oma") including components derived from glands ("adeno-") and muscle ("-my-"). It is a type of complex and mixed tumor.

The diagnosis of PASH is by biopsy.

The important differential diagnosis is angiosarcoma, from which it was first differentiated in 1986.

In urologic pathology, atypical small acinar proliferation, abbreviated ASAP, is a collection of small prostatic glands, on prostate biopsy, whose significance is uncertain and cannot be determined to be benign or malignant.

ASAP, generally, is "not" considered a pre-malignancy, or a carcinoma in situ; it is an expression of diagnostic uncertainty, and analogous to the diagnosis of ASCUS (atypical squamous cells of undetermined significance) on the Pap test.

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.

Benign and borderline variants of this neoplasm are rare, and most cases are malignant.

These tumors may have a worse prognosis than serous tumors.

Carcinoma "in situ (CIS), also known as in situ" neoplasm, is a group of abnormal cells. While they are a form of neoplasm there is disagreement over whether CIS should be classified as cancer. This controversy also depends on the exact CIS in question (i.e. cervical, skin, breast). Some authors do not classify them as cancer, however, recognizing that they can potentially become cancer. Others classify certain types as a non-invasive form of cancer. The term "pre-cancer" has also been used.

These abnormal cells grow in their normal place, thus ""in situ"" (from Latin for "in its place"). For example, carcinoma "in situ" of the skin, also called Bowen's disease, is the accumulation of dysplastic epidermal cells within the epidermis only, that has failed to penetrate into the deeper dermis. For this reason, CIS will usually not form a tumor. Rather, the lesion is flat (in the skin, cervix, etc.) or follows the existing architecture of the organ (in the breast, lung, etc.). Exceptions include CIS of the colon (polyps), the bladder (preinvasive papillary cancer), or the breast (ductal carcinoma "in situ" or lobular carcinoma "in situ").

Many forms of CIS have a high probability of progression into cancer, and therefore removal may be recommended; however, progression of CIS is known to be highly variable and not all CIS becomes invasive cancer.

In the TNM classification, carcinoma "in situ" is reported as TisN0M0 (stage 0).

These terms are related since they represent the steps of the progression toward cancer:

- Dysplasia is the earliest form of precancerous lesion recognizable in a biopsy. Dysplasia can be low-grade or high-grade. High-grade dysplasia may also be referred to as carcinoma "in situ".

- Invasive carcinoma, usually simply called cancer, has the potential to invade and spread to surrounding tissues and structures, and may eventually be lethal.

Typically, they are cystic neoplasms with polypoid masses that protrude into the cyst. On microscopic pathological examination, they are composed of cells with clear cytoplasm (that contains glycogen) and "hob nail" cells (from which the glycogen has been secreted). The pattern may be glandular, papillary or solid.

Atypical ductal hyperplasia, abbreviated ADH, is the term used for a benign lesion of the breast that indicates an increased risk of breast cancer.

The name of the entity is descriptive of the lesion; ADH is characterized by cellular proliferation (hyperplasia) within one or two breast ducts and (histomorphologic) architectural abnormalities, i.e. the cells are arranged in an abnormal or atypical way.

In the context of a core (needle) biopsy, ADH is considered an indication for a breast lumpectomy, also known as a surgical (excisional) biopsy, to exclude the presence of breast cancer.

The most common location by far is the gingival margin and other areas of the masticatory oral mucosa, these occur more frequently in the fifth decade of life, and have good prognosis, the treatment of choice for oral VXs is surgical excision, and recurrence is rare.

The condition can affect other organs of body, such as the penis, vulva, and can occur in anal region, nose, the ear, lower extremity, scrotum.

ADH, generally, is asymptomatic. It usually comes to medical attention on a screening mammogram, as a non-specific suspicious abnormality that requires a biopsy.

Verruciform xanthoma is an uncommon benign lesion that has a verruciform (wart-like) appearance, but it may appear polypoid, papillomatous, or sessile. The verruciform was first described by Shafer in 1971 on the oral mucosa. Usually found on the oral mucosa of middle-aged persons, verruciform xanthomas have also been reported on the scrotum and penis of middle-aged to elderly Japanese males. While the most common site is the oral mucosa, lesions that occur elsewhere usually arise on the perineum or on the skin with some predisposing factor, such as lymphedema or an epidermal nevus.

There are two main types of cystitis glandularis, non-mucinous and mucinous (intestinal). The difference is in the cellular production of mucin, a normal feature of colonic and intestinal epithelial cells but not of urothelial cells. Another distinction is made between focal areas and diffuse involvement of the bladder. Whereas focal areas are more common, diffuse involvement is seen in chronically irritated bladders, such as in paraplegics or those with bladder stones or indwelling catheters. Individuals with diffuse intestinal-type cystitis glandularis are at increased risk for developing bladder cancer.