[Radiation-induced cutaneous hamartoma in a patient with Cowden syndrome. Clinical evidence for heterozygosity].

A 56-year-old woman had typical features of Cowden syndrome in the form of hamartomas involving the skin, lips, and oral mucosa. At the age of 48, a mastectomy was performed for adenocarcinoma with a regional metastasis, and X-ray treatment was applied to the left axilla. Subsequently the patient developed approximately 30 skin-colored nodules surrounding the irradiated axillary region within several months. Histopathological examination of one of these lesions showed characteristic features of sclerotic fibroma. The multiple radiation-induced fibrous hamartomas observed may be best explained by multiple events of loss of heterozygosity (LOH), because molecular studies in other patients with Cowden syndrome have shown that both benign and malignant tumors originate from LOH. The X-ray treatment would have induced LOH in many cells, giving rise to either homo- or hemizygosity for the Cowden mutation.