Description of the clinical case: A 65-year-old male leucodermic patient, accompanied at the Clinic of Surgery and Oral Medicine of the Faculty of Dental Medicine - University of Lisbon (FMDUL), with indication for multiple exodontia and posterior removable prosthetic rehabilitation. Medicated with enalapril maleate/lercanidipine hydrochloride and simvastatin for the control of hypertension and hypercholesterolemia. History of sinusitis, malaria and intestinal polyposis. Extraoral objective examination revealed multiple papular cutaneous lesions on the face. Intraorally, several asymptomatic papules on the dorsum of the tongue were also identified. The clinical condition was suggestive of Cowden syndrome or multiple hamartoma syndrome. The differential diagnosis of these lesions includes transient lingual papillitis, neurofibromatosis and multifocal epitelial hyperplasia (or Heck's disease), among other entities. An excisional biopsy of one of the lesions of the lingual mucosa was performed, whose anatomopathological examination confirmed fibroepithelial hyperplasia. Discussion: Cowden syndrome or multiple hamartoma syndrome is a rare autosomal dominant genetic condition, with alteration of the PTEN gene, which is found on chromosome 10. Its prevalence is only 1:200 000 cases and affects, generally, leucodermic females. It is characterized by the presence of several mucocutaneous hamartomatous lesions of ectodermal, mesodermal and endodermal origin. The pathognomonic criteria include multiple skin (trichilemmomas) and oral papules (fibromas), as well as palmar or plantar acral keratosis. Conclusion: Cowden syndrome is a relatively unknown entity in the medical community and, therefore, underdiagnosed in the population. Patients are at increased risk of malignant neoplasias in various organs and systems. Dentist plays a fundamental role in the diagnosis of oral manifestations of the disease. Keywords: cowden syndrome, multiple hamartoma, oral medicine and pathology, oral biopsy