Developmental disorders and malformations of the breast.

Developmental abnormalities and malformations of the breast are rare and encompass a variety of genetic, syndromic, acquired and sporadic conditions. Abnormalities in development may include irregularities in the nipple areolar complex and/or the underlying glandular tissue, resulting in under or overdevelopment of breasts. Age of presentation and clinical severity is dependent on the underlying biologic cause. Abnormalities may involve the entirety of unilateral or bilateral breasts, particularly in association with syndromic conditions or endocrine abnormalities. Disordered development may also be focal, resulting in tumor-like lesions such as hamartomas, pseudoangiomatous stromal hyperplasia and gynecomastia. In this review, we discuss the disorders of breast development including etiologies, clinical presentations and corresponding histopathologic features.