Extramammary Paget's disease overview

# Overview
Extamammary Paget's disease (EMPD) is a rare non-melanocytic intraepidermal skin lesion. It usually involves the epidermis, but occasionally extends into the underlying dermis. It has predilection for apocrine gland-bearing areas: mostly the perineum, vulva, axilla, scrotum and penis. Extramammary Paget's disease may be classified into two groups based on the origin of the Paget's cells. Extramammary Paget's disease may be classified into four subtypes based on site of origin and area affected. On gross pathology, plaque with an irregular border and erythematous or white lesion are characteristic findings of extramammary Paget's disease. On microscopic histopathological analysis, the presence of Paget's cells (large cells with abundant amphophilic or basophilic, finely granular cytoplasm and a large, centrally-located nucleus and prominent nucleolus) and signet ring cells are characteristic findings of extramammary Paget's disease. Extramammary Paget's disease is usually associated with adnexal apocrine carcinoma, which represents infiltration of the deeper adnexa by epidermal Paget cells. Neither the direct cause nor a prominent risk factor of extramammary Paget's disease has been identified. Extramammary Paget's disease is rare and the exact incidence is unknown. Extramammary Paget's disease commonly affects individuals 50-60 years of age. Females are more commonly affected with the disease than males. The female to male ratio is approximately 3-4.5 to 1. It usually affects individuals of the Caucasian race, but it may occur in other races. Symptoms of extramammary Paget's disease include pruritis, vulvar pain, vulvar bleeding, and burning sensation. Biopsy is diagnostic of extramammary Paget's disease. Other diagnostic studies for extramammary Paget's disease include fine needle aspirate and PAP smear. Treatment depends on the stage at diagnosis. Treatment often includes surgery and chemotherapy with either 5-fluorouracil, imiquimod, or combination of paclitaxel and trastuzumab.

# Historical Perspective
Extramammary Paget's disease was first discovered by Radcliffe Crocker in 1889.

# Classification
Extramammary Paget's disease may be classified into two groups based on the origin of the Paget's cells. Extramammary Paget's disease may be classified into four subtypes based on site of origin and area affected.

# Pathophysiology
On gross pathology, plaque with an irregular border and erythematous or white lesion are characteristic findings of extramammary Paget's disease. On microscopic histopathological analysis, Paget's cells which are large cells with abundant amphophilic or basophilic, finely granular cytoplasm, the nucleus which is usually large, centrally situated, and sometimes contains a prominent nucleolus, and signet ring cells are characteristic findings of extramammary Paget's disease. Extramammary Paget's disease arises from keratinocytic stem cells or from apocrine gland ducts. Approximately 25% (range 9-32%) of the cases of extramammary Paget's disease are associated with an underlying in situ or invasive neoplasm. Extramammary Paget's disease is usually associated with adnexal apocrine carcinoma, which represents infiltration of the deeper adnexa by epidermal Paget cells.

# Causes
The cause of extramammary Paget's disease has not been identified.

# Differential Diagnosis
Extramammary Paget's disease must be differentiated from basal cell carcinoma, Bowen's disease, cutaneous candidiasis, intertrigo, irritant contact dermatitis, lichen simplex chronicus, plaque psoriasis, tinea cruris, seborrhoeic dermatitis, lichen sclerosis, anogenital intraepithelial neoplasia, melanoma, histiocytosis, mycosis fungoides, leukoplakia, squamous cell carcinoma, condylomata accuminata, Crohn's disease, and hidradenitis suppurativa.

# Epidemiology and Demographics
Extramammary Paget's disease is rare, and its exact incidence is unknown. Extramammary Paget's disease commonly affects individuals 50-60 years of age. Females are more commonly affected with the disease than males. The female to male ratio is approximately 3-4.5 to 1. It usually affects individuals of the Caucasian race, but it may occur in other races.

# Risk Factors
There are no established risk factors for extramammary Paget's disease.

# Screening
According to the United States Preventive Services Task Force, screening for extramammary Paget's disease is not recommended among the general population.

# Natural History, Complications and Prognosis
If left untreated, the disease is usually progressive. Common complications of extramammary Paget's disease include recurrence of the tumor and metastasis. Depending on the extent of the tumor at the time of diagnosis, the prognosis may vary. The prognosis for primary extramammary Pagets's disease confined to the epidermis is excellent.  However, invasive primary extramammary Paget's disease carries a poor prognosis, particularly if lymphovascular invasion is present.

# Diagnosis

## History and Symptoms
Symptoms of extramammary Paget's disease include pruritis, vulvar pain, vulvar bleeding, and burning sensation.

## Physical Examination
Common physical examination findings of extramammary Paget's disease include well demarcated, erythematous or leucoplakic plaques present on the skin, characteristic cake-icing appearance of vulval extramammary Paget's disease (erythematous changes associated with white islands and bridges of hyperkeratotic epithelium), and lymphadenopathy.

## Chest X Ray
Chest x-rays may be performed to detect metastases of extramammary Paget's disease to the lungs.

## CT
Chest, abdomen, and pelvic CT scan may be helpful in the diagnosis of extramammary Paget's disease. CT scan can confirm the exact location of the cancer and show the organs nearby, as well as lymph nodes and distant organs where the cancer might have spread.

## MRI
Chest, abdomen, and pelvic MRI scan may be helpful in the diagnosis of EMPD.

## Other Imaging Findings
Other imaging studies for EMPD include bone scan, ultrasound scan, PET scan, cystoscopy, sigmoidoscopy, colonoscopy, mammography, and colposcopy, which demonstrates metastases and underlying invasive carcinomas.

## Other Diagnostic Studies
Biopsy is diagnostic of extramammary Paget's disease. Other diagnostic studies for extramammary Paget's disease include fine needle aspirate and Pap smear.

# Treatment

## Medical Therapy
Treatment depends on the stage at diagnosis. Chemotherapy with either 5-fluorouracil, imiquimod, or combination of paclitaxel and trastuzumab has been evaluated for the treatment of extramammary Paget's disease.

## Surgery
Surgery is the first line treatment for extramammary Paget's disease.

## Primary Prevention
There are no primary preventive measures against extramammary Paget's disease.

## Secondary Prevention
Secondary prevention strategies following extramammary Paget's disease include an annual complete physical examination, proctosigmoidoscopy and punch biopsy of any new lesion. Colonoscopy should be carried out at every two to three year intervals.