The paper reports the case of rare paraneoplastic dermatosis, acrokeratosis paraneoplastica (Bazex syndrome) in a 60-years-old patient diagnosed with adenocarcinoma of the sigmoid colon. The diagnosis of Bazex syndrome was evidenced by erythematous-squamous and hyperkeratotic acral lesions and onychodystrophy of the feet and hands, along with resistance to antimycotic and anti-inflammatory therapy, elderly age of the patient, and long-term tobacco abuse. Skin biopsy revealed nonspecific inflammatory changes and ruled out psoriatic abnormalities. Gastrointestinal examination was carried out in view of the increased value of TU M2-PK tumor marker and revealed adenocarcinoma, which developed in the adenomatous polyp of the sigmoid colon. After tumor resection, dermatological manifestations of the disease began to regress. We applied a diagnostic algorithm that includes clinical, laboratory, and therapeutic measures, which enabled us to diagnose a patient with acrokeratosis paraneoplastica (Bazex syndrome) associated with the early stage of the sigmoid colon cancer.