Case 6 -

Atypical Lobular Hyperplasia Involving Sclerosing Adenosis Jean F Simpson, MD Department of Pathology, Vanderbilt University Medical Canter Nashville, TN

Case History A 37 year old woman underwent a stereotactic core needle biopsy of an area of microcalcifications. Case 6 - Figure 1 Click to view with ImageScope Click to view with a Web-Based Viewer Microscopic Appearance The needle biopsy specimen shows areas of sclerosing adenosis that contain the determinant microcalcifications. Incidental to this finding, many of the areas of adenosis contain a proliferation of monomorphic cells filling and partially expanding these acini. Where the sclerotic process is well developed, some of the acini are compressed, and can be misinterepreted for an invasive process. The proliferation is characterized by cells that have round, regular nuclei with inconspicuous nucleoli, and homogenous pale cytoplasm, and occasional intracytoplasmic lumina. In these areas there are no well-developed cell borders; the cells grow in a dyshesive manner. Final Diagnosis Atypical lobular hyperplasia involving sclerosing adenosis Discussion and Clinical Implications The cellular proliferation is readily recognized as a lobular neoplastic process. Because there is minimal distension, and no distortion of involved spaces, atypical lobular hyperplasia is the appropriate diagnosis rather than lobular carcinoma in situ. From a diagnostic point of view, recognizing the background of sclerosing adenosis is essential in avoiding the misdiagnosis of invasive carcinoma. Some have advocated using immunohistochemical markers of basement membrane material to highlight the benign nature of the sclerotic arrangement of these spaces. Others use p63 to highlight often inconspicuous benign elements. A single study has shown that atypical lobular hyperplasia is three times more likely to be present in a biopsy if there is also sclerosing adenosis present. [1] Both of these cases illustrate atypical lobular hyperplasia presenting on needle core biopsy specimens, in a setting that is not characteristic for atypical lobular hyperplasia. Careful attention to the underlying process will avoid over-diagnosing ALH. Reference: Jensen RA, Page DL, Dupont WD, Rogers LW. Invasive breast cancer risk in women with sclerosing adenosis; Cancer 1989; 64:1977-83.