Cowden syndrome is a rare hereditary disease. Incidence of the disease is conditioned by occurrence of mutations in the PTEN gene. The disease has a frequency of 1/120,000 newborn and it predisposes to the occurrence of hamartoma polyps in the gastrointestinal tract, skin tumours, as well as tumours of the breast, ovary and thyroid. Here we describe the case of a Polish patient diagnosed with Cowden syndrome with an identified mutation in the PTEN gene. The disease course of the patient is described and discussed along with other cases of carriers of substitution 68T>A in the PTEN gene.