Merkel Cells and Merkel Cell Carcinoma of Genitourinary System Tumor with Aggressive Behavior and Poor Prognosis

Abstract

Human Merkel cells (MCs) were first described by Friedrich S. Merkel in 1875 and named "Tastzellen" (touch cells). Merkel cells are primarily localized in the basal layer of the epidermis and concentrated in touch-sensitive areas. Their density varies among each anatomical site. Mostly they are concentrated in the palms of hands, predominantly in the finger pads, also in the soles and toes than in any other parts of the body. Concentration of MC in the external genitalia has not been studied, but some researchers detected some MCs in the male prepuce and in the female clitoris. Last year they were first described in the labia minora. Functionally they can be classified into some subpopulations with different functions: mechanoreceptive, endocrine, chemo sensitive. They belong to mechanoreceptors detecting tissue deformations and release various neurotransmitters to nerve endings. Tumor arising from Merkel cells called Merkel cell carcinoma (MCC). This highly aggressive malignancy occurs most often in the elderly white peoples on the skin of the head, neck and extremities. Its incidence is generally higher in men than in women. The rate of mortality is higher than in patients with melanoma and prognosis is rather poor. MCC of the genitourinary system are very rare, aggressive and may be misinterpreted with other cancers of genitourinary system. Most cases of MCC reported in the English literature in the women are in the vulva. In general MCC have an aggresive behavior, but those in the vulva are virulent with a 100% rate of inguinal node and also distant metastases. Prognosis of this carcinoma is very poor than prognosis of the MCC arising in other parts of the body.