The association between acanthosis nigricans (malignant type) and internal malignant tumour is well established. In the majority of cases the malignant tumour is localized to the gastrointestinal tract or the thoracic cavity. The malignant tumour is believed to be an adenocarcinoma in most cases. A case of malignant acanthosis nigricans associated with a follicular adenocarcinoma of the thyroid gland in a 31-year-old white male with congenital hypothyroidism and eruptive xanthomas due to hyperlipoproteinemia of type V (Frederickson) is reported.