Glycogen-rich clear cell breast carcinoma: HER2-positive early-stage case with disease-free follow-up

What happened, in summary

This 66-year-old woman found a lump in her left breast during self-examination. Ultrasound showed a 9 by 10 millimeter mass with an uneven shape and irregular margins in the upper outer breast, and mammography also showed a suspicious focal asymmetry. Because she had a severe allergy to local anesthetics, she chose total mastectomy with axillary lymph-node removal rather than diagnostic biopsy under local anesthesia. Surgery revealed a 13-millimeter invasive tumor composed almost entirely of clear cells arranged in nests and tubules. Under the microscope, the tumor cells had abundant clear cytoplasm and sharply defined cell borders. Special staining showed intracytoplasmic glycogen, confirming glycogen-rich clear cell carcinoma, a rare breast cancer subtype. The tumor was estrogen receptor positive, progesterone receptor negative, and HER2 positive, with a Ki-67 proliferation index of about 10%. The removed lymph nodes were negative, supporting Stage I disease. Because the subtype is rare and can overlap visually with other clear-cell tumors, the pathology workup was central to confirming that this was a primary breast cancer. The final diagnosis also explained why treatment needed to address both hormone sensitivity and HER2 positivity. This made adjuvant planning especially important. After surgery, she received weekly paclitaxel plus trastuzumab for 1 year as HER2-directed adjuvant therapy. She then received radiotherapy and started letrozole, an endocrine therapy used for estrogen receptor-positive breast cancer. Her care combined surgery, chemotherapy, HER2-targeted antibody therapy, radiation, and hormone therapy to reduce the chance of recurrence. At 1-year follow-up, she remained disease-free with no evidence of cancer recurrence.