Cowden's disease is characterized by multiple hamartomas and neoplasias of ectodermal, mesodermal and endodermal origin. A case of a 22-year-old man suffering from nocturnal dyspnoea is reported. The patient had a large number of hyperkeratotic, lichenoid papules, scattered over the right side of the trunk, back and palm. In his oral cavity, papules were present on the gingiva and hard palate. The patient was operated on for tonsillar hypertrophy and for excluding the possibility of malignant lymphoma. An examination of immunophenotypes of the palatal tonsil lymphocytes revealed B-cell proliferation and poly-clonal immunoglobulin.