Similarities of cutaneous and breast pathology in Cowden's Syndrome.

Cowden's Syndrome (CS), or multiple hamartoma syndrome, is an autosomal dominant disorder characterized by mucocutaneous lesions, multiple benign tumors of internal organs and an increased risk of breast cancer. Here, we describe and illustrate in detail the benign breast pathology of 59 breast cases from 19 women with CS. Fibrosis is a significant characteristic of the breasts of patients with CS. Fibroadenomas appear to hyalinize at an early age and are frequently complex. The specimens demonstrate a spectrum of dense hyalinization of both the lobule and the stroma, and hyaline nodules appear to be the most characteristic lesion. This hyalinization process shares striking similarities with keloids, as well as the sclerotic nodules seen in the skin of CS individuals. Ductal carcinoma in CS was common, and it appeared to be associated with stromal hyalinization. Other frequently found benign features are adenosis and cysts. Of interest, the features of the benign breast disease in CS show certain similarities with senescent lobules, fibrous mastopathy of diabetes mellitus, and mammary hamartomas. These observations provide a framework for pathologists to identify this underrecognized syndrome.