Metastatic invasive lobular breast carcinoma to pancreas: biliary stent and paclitaxel

What happened, in summary

A 41-year-old woman was first treated for left breast invasive lobular carcinoma in December 1994 after a mass was found in the upper outer breast with a palpable axillary lymph node. Mammography and ultrasound showed 2 suspicious left-breast masses about 3 cm apart, and the initial workup found no distant metastases. Fine-needle aspiration confirmed invasive lobular breast carcinoma. She had a modified radical mastectomy. Final pathology showed 2 invasive lobular tumors measuring 2 cm and 1 cm, with 1 of 15 level 1 axillary nodes involved. The primary tumor was ER-negative, PR-negative, HER2-negative, and Ki-67 was 30%. She received adjuvant chemotherapy and radiotherapy, then remained in complete remission for 21 years with regular follow-up. In June 2020, she presented with severe lower-back pain, jaundice, nausea, and 9 kg of weight loss over 3 months. CT showed a 2.6 x 2.1 cm pancreatic-head lesion with biliary-tree dilation and enlarged coelio-mesenteric lymph nodes. Mammography did not show a new breast lesion, and pancreatic tumor markers were not elevated. Biopsy of the pancreatic lesion showed poorly differentiated carcinoma with GATA and ER nuclear expression, supporting metastatic lobular breast carcinoma rather than a new pancreatic primary. She received an endoscopic biliary stent and palliative paclitaxel, but treatment stopped after only 2 courses because her general condition deteriorated. She was then lost to follow-up. At recurrence, liver tests also supported biliary obstruction, with total bilirubin 70 umol/L and marked ALT and AST elevation. The absence of elevated pancreatic tumor markers and the breast-lineage staining helped keep the diagnosis anchored to metastatic breast cancer rather than a new pancreatic cancer.