An 83-year-old Chinese woman noticed a palpable mass in the left breast that had been there for 8 months. When the woman first came, there was a round mass about 3 cm in size in the inner upper quadrant and the outer upper quadrant of the left breast, without local pain, skin redness, swelling, ulceration, nipple bleeding, or discharge. She had histories of hypertension and diabetes for 7 years and was diagnosed with diabetic nephropathy, chronic kidney disease stage 4, and renal anemia for 3 months, and all the diseases were under treatment and control. She had no family history of tumor disease. Due to the patient's old age and multiple underlying diseases, no further treatment was performed. Eight months later, she felt a persistent dull pain in her breast for 10 days. The physical examination showed that the left breast was enlarged, and there was a firm, irregular mass, about 7 cm x 8 cm size in the left breast, with unclear boundaries and an acceptable range of motion without other changes in the breast. No mass was found in the right breast, and no enlarged lymph nodes were touched on the bilateral axillary and supraclavicular region.
The laboratory tests showed that hemoglobin was 76 g/L, alkaline phosphatase was 554 U/L, and the serum tumor markers were all in a normal range. A calcified mass was found at the first examination of ultrasonography (US) and computed tomography (CT) plain scan and contrast enhancement of chest (Figure 1). The lesion was considered to be a degenerative fibroadenoma and was classified as a benign tumor according to Breast Imaging and Reporting Data System (BI-RADS) category 3. After 8 months, it was presumed to be highly malignant and graded as BI-RADS category 4C because of its rapid growth and more calcifications at the examination of US and CT plain scan and contrast enhancement of chest (Figure 1). Biopsy was performed according to the patient's preference, resulting in specimens showing to be a malignant phyllodes tumor of the breast with ossification or osteosarcoma. Then, 99mTc-MDP whole-body bone imaging was performed, and it showed that there was a mass-like abnormal radioactive concentration of Tc-99m outside the bone of the left chest, without other abnormal concentrations (Figure 2). Mastectomy and axillary lymph node dissection was performed on the left breast, and the histological results were observed (Figure 3). Microscopically, it showed a 7 cm x 8 cm x 8 cm regular mass in the central region with a clear boundary:the pectoralis major was invaded. The tumor was rich in osteoid tissues, heteromorphic osteoblast-like cells, multinucleated giant cells, and small foci of cartilage, which is consistent with osteosarcoma. Immunohistochemical analysis showed Special AT-rich-binding protein 2 (SATB2) (+), Vimentin (+), CK-Pan (AE1/AE3) (-), CK-Low Molecular Weight (CK-LMW) (-), CK-High Molecular Weight (CK-HMW) (-), CK56 (-), CK14 (-), P63 (scattered +), P53 (+-), S-100 (-), desmin (des) (-), Smooth Muscle Actin (SMA) (-), Cam5.2 (-), CD10 (-), CD34 (-), CD117(-), CD68 (scattered +), Estrogen receptor (ER) (-), progesterone receptor (PR) (-), Human Epidermal growth factor Receptor 2 (Her-2) (-), and Ki-67 (+, 60%). Axillary lymph node was negative (0/10). After the operation, she did not have any further treatment because of her venerable age. Four months later, she died of respiratory failure caused by multiple lung metastases (Figure 4).