Skeletal Muscle Metastases from Breast Cancer: Two Case Reports
A 51-year-old woman was referred to Division of Medical Oncology on March 23, 2011, for elevated serum levels of the tumor marker CA 15-3. At that time, she had been taking tamoxifen (20 mg daily) for 6 months following mastectomy in 2009. She had no symptoms and there was no clinical evidence of tumor recurrence on the breast computed tomography (CT) scan, bone scan, and F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) performed in February 2011.\nThe woman's medical history showed that she had been diagnosed with right breast cancer (cT2N2M0) in January 2009, and underwent modified radical mastectomy after three cycles of neoadjuvant chemotherapy with docetaxel and epirubicin. An histopathological examination showed invasive ductal carcinoma with nuclear grade 3, and 4 metastatic lymph nodes out of the 5 dissected axillary lymph nodes. Immunohistochemistry studies showed positive staining for the estrogen receptor (ER) protein, and negative staining for progesterone receptor (PR) protein and the human epidermal growth factor receptor 2 (HER2) (score 0). She received an additional three cycles of adjuvant chemotherapy with docetaxel and epirubicin until June 2009, and then adjuvant radiotherapy on the right chest wall and regional lymphatics. In November 2009, a 2.3-cm diameter mass was found on surveillance CT of the left breast, and invasive ductal carcinoma was confirmed by core needle biopsy (cT2N2M0). She underwent modified radical mastectomy of her left breast. An histopathological examination revealed invasive ductal carcinoma with nuclear grade 2 and lymphovascular invasion. There were 5 lymph node metastases detected in 9 resected axillary lymph nodes. The expression of ER, PR, and HER2 was concordant with the prior right breast cancer: ER positive, PR negative, and HER2 negative (score 0). She received adjuvant radiotherapy and six cycles of adjuvant chemotherapy with cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) until October 2010.\nHer serum level of CA 15-3 increased from 24.10 U/mL in October 2010 to 121.94 U/mL (normal range, 0-28 U/mL) in March 2011, when she was presented to our department. Because there was no clinical evidence of tumor recurrence, we planned to carefully follow up tumor markers and imaging tests. Her serum level of CA 15-3 continued to increase to 829.77 U/mL in August 2011, but there was no evidence of tumor recurrence on the chest CT and bone scan, performed in April and July 2011. In October 2011, she complained of intermittent stabbing pain in the epigastric area. On physical examination, there was no palpable mass in her abdomen, but she had mild tenderness with deep palpation in the epigastric region. We performed chest and abdominal CT scans and PET/CT. CT scans showed multiple round or oval masses with the density of soft tissue in the subcutaneous and rectus abdominis muscle of the epigastric region (), and enlargement of lymph nodes in the peripancreatic and para-aortic regions. PET/CT also showed multiple nodules of various sizes with increased FDG uptake (SUVmax, 7.1) in the upper anterior abdominal muscles (), and multiple enlarged lymph nodes with increased FDG uptake (SUVmax, 4.3) in the upper para-aortic region. A core needle biopsy of the abdominal wall mass was performed, and a pathological examination revealed metastatic carcinoma (), that was positive for ER, negative for PR, and positive for HER2 (score 3). Thus, the HER2 status was discordant between the primary breast cancer and the metastatic carcinoma. She received six cycles of trastuzumab and docetaxel chemotherapy followed by three cycles of trastuzumab monotherapy. After the third and sixth cycles of combination chemotherapy, follow-up CT scans showed partial regression of multiple metastatic masses in the subcutaneous and rectus abdominis muscles. However, after an additional three cycles of trastuzumab monotherapy, follow-up CT scans showed an increase in size of the metastatic carcinoma in the subcutaneous and rectus abdominis muscles, and her disease progressed. She therefore started second-line capecitabine and lapatinib combination chemotherapy in June 2012.