Single external oblique muscle metastasis of breast invasive lobular carcinoma: a case report

We reported a 59-year-old female who diagnosed with right breast invasive lobular carcinoma (pT2N0M0, stage IIA) and received modified radical mastectomy with adjuvant chemotherapy and radiotherapy (50 Gy) in 1999. But, she found T10-spine metastasis and received palliative radiotherapy (30 Gy in 10 fractions) 3 years later. In 2012, she had a left abdominal mass and received abdominal wall tumor resection and a metaplastic invasive lobular carcinoma [estrogen receptor (ER)(+), progesterone receptor (PR)(−), human epidermal growth factor receptor 2 (HER2)(−) with positive surgical margin] was noted by pathological reports. In spite of hormone therapy, she experienced a left abdominal painless mass at the same location underneath the previous surgical scar in 2016. After surgical excision, computed tomography showed a residual left external oblique muscle 4.8 cm × 5.0 cm mass. Under the impression of right breast cancer with left external oblique muscle metastasis [metastatic invasive lobular carcinoma, rcT0N0M1, rpT0N0M1, stage IV (AJCC 7th staging)], she received post-operative radiotherapy 60 Gy in 30 fractions. She continued to receive chemotherapy and no evidence of abdominal recurrence till now.