Introduction: Involvement of pre-existing benign lesions by ductal carcinoma in situ (DCIS) or lobular neoplasia (LN) can present difficult diagnostic challenges, and can easily cause misdiagnosis of invasive carcinoma and over-management of localized disease. Our objective was to gather the largest case series of DCIS and LN involving sclerosing adenosis (SA), and to report the characteristic features of these lesions, in order to provide histologic criteria for the diagnostician.
Methods: Our database was searched for core biopsy material diagnosed as carcinoma in situ involving adenosis. Glass slides and pathology reports were reviewed. The cases were studied for salient features, and clinical follow-up was also obtained.
Results: Thirty-one cases of DCIS or LN involving SA were obtained (12 cases of DCIS, 19 cases of LN including LCIS and ALH). Histomorphologic features commonly seen with DCIS or LN involving SA included lobulocentric architecture (31/31, 100%), myoepithelial cells visible by H&E at least focally (31/31, 100%), and separate areas of SA not involved by neoplasia (29/31, 93.5%). Features that were sometimes seen included hyaline basement membranes surrounding the lesion (14/31, 45.2%), DCIS/LN apart from the area of involvement by SA (16/31, 51.6%), and calcifications associated with DCIS/LN/SA (12/31, 38.7%). Features that were not commonly seen included desmoplasia (6/31, 19.4%), dense inflammation (4/31, 12.9%), and single epithelial cells enveloped by flattened myoepithelial cells (6/31, 19.4%). Of the ten cases of DCIS with known follow-up, four showed DCIS involving either SA or a complex SA on excision (4/10, 40%), four had only DCIS (4/10, 40%), one had DCIS with a small 1.8-mm focus of predominantly tubular carcinoma (1/10, 10%), and one showed invasive ductal carcinoma on excision (1/10, 10%). The latter case of invasive ductal carcinoma occurred in a patient who had a delay of 3 years from diagnosis to surgical resection. Of the eight cases of LN with surgical follow-up, seven had LCIS (7/8, 87.5%), and one showed only fibroadenoma and SA with no residual LN in the excised specimen (1/8, 12.5%). Importantly, no invasive carcinoma was identified in any of the resections for LN involving SA.
Conclusions: In our series of carcinoma in situ (CIS) involving sclerosing adenosis diagnosed on core biopsy, lobular lesions involving SA were more common than ductal lesions. Ductal and lobular carcinoma in situ involving adenosis were best diagnosed by the low-power appearance of a lobulocentric pattern of growth. The most helpful diagnostic feature was the observation of additional foci of carcinoma in situ away from the adenosis. Immunohistochemical stains for myoepithelial cells were useful in particularly difficult cases. The presence of stromal desmoplasia does not preclude the diagnosis of carcinoma in situ involving adenosis. Knowledge of these diagnostic pearls can reduce over-interpretation of CIS on core biopsy and subsequent overtreatment.
Keywords: Adenosis; Breast; Core biopsy; Ductal carcinoma in situ; Lobular carcinoma in situ.