In the literature, Marjolin's ulcers are defined as skin cancers that develop secondarily in areas susceptible to an injury, seized by a chronic inflammation or covered by scar tissue.This paper presents three clinical cases of spinocellular carcinoma, which occurred around long-standing venous ulcers or chronic traumatic skin injury within the lower limbs. All the patients had their limbs amputated. No clinical or radiological qualities of lymphadenopathy were diagnosed. The latest checkups indicated the patients' good condition without traits of the neoplastic disease.Managing patients with chronic ulcers, regardless of their aetiology, requires that the doctor should have increased oncological alertness. In this case, one of the most important elements of diagnostics is a regular histopathological assessment of the lesion. Only this procedure enables the early and efficacious surgical treatment of potential secondary neoplastic lesions and possible saving of the limb.