Pathology

A variety of changes may be noted including:

• cysts:
  • microcysts - less than 1 cm in diameter
  • macrocysts - up to 5 cm in diameter; includes the blue domed cysts of Bloodgood which unopened, appear brown to blue due to the contained fluid
• apocrine metaplasia - the normal ductular epithelium that lines the cyst proliferates to resemble that of apocrine sweat glands
• fibrosis - proliferation of fibrous tissue without epithelial change
• adenosis:
  • simple adenosis - hyperplastic proliferation of lobular acini / ductules
  • sclerosing adenosis - proliferation of fibrous tissue accompanies that of the acini, splitting them apart

Reference

1. Rosa M, Agosto-Arroyo E. Core needle biopsy of benign, borderline and in-situ problematic lesions of the breast: Diagnosis, differential diagnosis and immunohistochemistry. Ann Diagn Pathol. 2019 Dec;43:151407.