Invasive Breast Carcinoma Arising in Microglandular Adenosis: Two Case Reports
Case 1 was a 44-year-old woman with a previous history of breast-conserving surgery because of ductal carcinoma in situ (DCIS) in her right breast 4 years ago. After breast-conserving surgery, she received radiotherapy on her right breast but no hormonal therapy or chemotherapy. During a regular follow-up, ultrasound examination revealed an abnormal nodular lesion in her left breast. She had no symptoms or signs associated with a breast mass. On physical examination, no palpable mass was found in either breast. Mammography showed heterogeneously dense breast tissue and a newly developed small nodular density at the left upper outer quadrant of the breast (). Ultrasound examination revealed an ill-defined irregular hypoechoic nodule measuring approximately 8 mm and an ill-defined hypoechoic nodule measuring approximately 7 mm (BI-RADS category 4b) at the 1 to 2 o'clock region and 5 cm from the left nipple. Both nodules were adjoining (). Ultrasound guided localization excisional biopsy and frozen section revealed that the lesion was invasive carcinoma. She underwent modified radical mastectomy (MRM) with sentinel lymph node biopsy (SLNB). No definite mass-like lesion was found on gross examination (). Microscopic examination revealed widely spread round proliferative glands lined by a single layer of flat to cuboidal epithelial cells and lacking a myoepithelial layer, indicating typical MGA. In part of the lesion, the glandular lumen was obliterated by proliferation of monotonous, atypical small cells with frequent mitotic figures, indicating carcinoma in situ. A cord-like arrangement and irregular aggregates of highly atypical cells were scattered in the stroma and extended into the adipose tissue (). Immunohistochemical (IHC) staining revealed the following: S-100 protein (+), estrogen receptor (ER) (-), progesterone receptor (PR) (+, Allred score 3), human epidermal growth factor receptor 2 (HER2) (-), lysozyme (+), α1-antitrpysin (+), calponin (-), and p63 (-). The SLNB showed no evidence of metastasis. The final diagnosis was multifocal invasive carcinoma associated with DCIS (grade 3) arising in MGA with stage 1A, T1 (<1 cm, in the largest one), N0 (0/1), M0, and lymphovascular invasion (-). After surgery, she received adjuvant chemotherapy and hormonal therapy. After 14 months of medical follow-up, no evidence of recurrence has been found.