# Pathology

Pathology

This can be considered in three phases: lobule development at 15–25 years, cyclical changes at 15–50 years and involution at 35–55 years of  age. It is believed that lobular proliferation leads to the formation of  fibroadenoma and involution leads to cyst formation. Aberration in the above phases may lead to a number of  benign conditions. /uni25CF Hyperplasia of  the epithelium is defined as the presence of  more than two layers of  cells in the lining of the ducts and acini. It may occur with or without atypia. If  atypia of  epithelial cells is seen, the terms atypical ductal hyperplasia (ADH) and atypical lobular hyperplasia (ALH) are used. If  features of  ADH are seen to involve more than two ducts or lesions measure >2 /uni00A0 mm in diameter, the term ductal carcinoma situ (DCIS) is used. /uni25CF Papilloma . Localised hyperplasia of  the ductal epi thelium may produce a papilloma within the ducts. It is composed of  a central fibrovascular core and papillary projections of  the epithelium and myoepithelial cells. The papillary lesions in a duct are of  three types: /uni25CF solitary papilloma (relative risk [RR] for cancer 1.5–2); /uni25CF papillomatosis: five or more papillomas in many ducts with peripheral and often bilateral distribution (RR for cancer 3); /uni25CF juvenile papillomatosis, also called Swiss cheese disease , a ff ects young women, who present with multiple firm palpable nodules; microscopically , there are multiple papillomas with/without atypia, apocrine cysts, ductal hyperplasia and sclerosing adenosis. A positive family history of  breast cancer increases the lifetime cancer risk. /uni25CF Cyst formation . Kinking or narrowing of  ductules is usually due to involution of  the stroma and may result in accumulation of secretions in the lobules, forming a micro cyst. Many microcysts may join together to form a macro cyst.