Benign sweat gland tumour. Light micrograph of a section through a vulva showing hidradenoma papilliferum (purple lobes). This condition is a benign (non-cancerous) growth of apocrine sweat glands. It usually produces a painless lump, which may form an ulcer. A biopsy is necessary to ensure that the lump is not a cancerous carcinoma. Magnification unknown.