The black spot is most likely a mole. Moles are due to abnormal accumulation of skin cells called melanocytes which secrete pigment called melanin. Melanin is a naturally occurring skin pigment which plays an important role in protecting skin harmful ultraviolet and ionizing radiations of sun light. Excessive production of this melanin pigment due to accumulated melanocytes imparts black/dark brown color to the mole. Although most moles are harmless, they can also be precursors for skin cancer called melanoma. So, I suggest you to consult a gynecologist or dermatologist for examination.
Few signs like increasing size of the mole or change in color, shape and texture of the skin can indicate possibility of a cancerous condition. Any such signs should be brought to immediate notice of doctor. Biopsy can be done for any tissue signs of cancer. Precancerous or early malignancy on biopsy warrants immediate treatment. Usually resection of the mole is adequate if the cancer cells are limited to upper layers of skin. Sometimes follow up chemotherapy or radiotherapy might be required if the lesion has penetrated deeper layers or metastasized locally.
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