A 67-year-old patient was admitted for diabetes mellitus. Incidentally a large ulcerating tumour was found on the right upper leg. The patient had been suffering from the lesion for six years but had never dared to show it to her physician. Notwithstanding negative outcome of thin needle aspiration oncological dissection was carried out. Histopathological examination proved the tumour to be a malignant clear cell hidradenoma, which is a rare eccrine tumour. This tumour is known to be aggressive and easily spreads to locoregional lymph nodes. Even though it is a rare disease, the aggressive behaviour and the poor prognosis warrant alertness to this neoplasm.