Aim: To present a case of a very rare malignant head and neck tumor – malignant eccrine spiradenoma, describe the clinical and pathological characteristics of the tumor, as well as the importance of early diagnosis with respect to the ultimate outcome of these treatments. Case report: This paper describes the case of a 46-year-old patient who was di- agnosed with hemangioma of the left side of the neck, and was followed for 25 years. Few months before the patient came to the Clinic, the lesion suddenly began to change. Based on the neck ultrasound, fine-needle cytopuncture, MRI and biopsy a suspicion on a metastasis of unknown primary tumor was established. PET / CT has not discovered the location of the primary tumor and only surgery and histopathologic verification of operating sample established the definitive diagnosis of malignant eccrine spiradenoma with metastasis in a single regional lymph node. The patient was treated with postoperative radio- and chemotherapy. Six months after the treatment, multiple metastases of the lung, pleura, mediastinum, and liver were found and 3 months later fatal outcome occurred. Discussion and conclusion: In the majority of cases this rare tumor is caused by malignant transformation of benign eccrine spiradenoma, although it can appear de novo. It rarely occurs in the head and neck region. Diagnosis is based on pathohistological findings. The tumor shows a strong preference to local and regional recurrence and to distant metastases, the prognosis of which is poor. It is important to diagnose the disease at an early stage when there is no regional or distant spread because at that stage the survival rate is very high.