Gastrointestinal metastasis from invasive lobular carcinoma with acquired ESR1 mutation: a case report
4 affiliations
- 1Department of Oncology, the Second Affiliated Hospital of Dalian Medical University, Dalian, China
- 2Department of Physical Examination Center, the Second Affiliated Hospital of Dalian Medical University, Dalian, China
- 3Department of Pathology, the Second Affiliated Hospital of Dalian Medical University, Dalian, China
- 4Department of Radiology, the Second Affiliated Hospital of Dalian Medical University, Dalian, China
Abstract
Background: Breast invasive lobular carcinoma (ILC) with multiple organ metastases at initial diagnosis is rare. This study reports a case of ILC presenting with bone marrow and bone metastases at first diagnosis, in which the patient developed gastrointestinal metastases (GIMs) one year later, and reviews the relevant literature.
Case Description: A 35-year-old female patient presented with a left breast mass accompanied by enlarged left axillary and cervical lymph nodes as well as thoracolumbar pain. Pathological biopsy confirmed the diagnosis of estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-low ILC, with metastases to the left axillary and cervical lymph nodes, bone marrow, and bone. The patient achieved tumor remission following treatment with endocrine therapy combined with a CDK4/6 inhibitor. One year later, she developed gastrointestinal symptoms such as nausea and vomiting. Pathological biopsy confirmed GIM from ILC, and the metastatic tumors harbored an ESR1 mutation (ESR1M) at p.Y537N. After treatment with the anti-HER2 antibody-drug conjugate (ADC) trastuzumab deruxtecan (T-DXd), disease control was achieved.
Conclusions: Although ER-positive and HER2-low ILC can derive clinical benefit from endocrine therapy combined with a CDK4/6 inhibitor, the tumor may still undergo occult progression, such as ESR1M and GIM. This case highlights the importance of dynamic biomarker monitoring and repeat biopsy when occult progression is suspected. Anti-HER2 ADC therapy may provide disease control and clinical benefit in selected patients with HER2-low ILC after endocrine resistance.
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BibTeX
@article{long2026gastrointestinal,
title = {{Gastrointestinal metastasis from invasive lobular carcinoma with acquired ESR1 mutation: a case report}},
author = {Zhouximao Long and Jinfeng Guan and Linlin Han and Jixia Kong and Qian Cao and Jizhuo Gao and Yi Liu and Mengyao Huang and Shun Wang and Man Li and Lingzhi Xu},
journal = {Translational Breast Cancer Research},
year = {2026},
month = jun,
doi = {10.21037/tbcr-2026-0019},
url = {https://doi.org/10.21037/tbcr-2026-0019},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Gastrointestinal metastasis from invasive lobular carcinoma with acquired ESR1 mutation: a case report
AU - Zhouximao Long
AU - Jinfeng Guan
AU - Linlin Han
AU - Jixia Kong
AU - Qian Cao
AU - Jizhuo Gao
AU - Yi Liu
AU - Mengyao Huang
AU - Shun Wang
AU - Man Li
AU - Lingzhi Xu
PY - 2026
DA - 2026/06/15
JO - Translational Breast Cancer Research
DO - 10.21037/tbcr-2026-0019
UR - https://doi.org/10.21037/tbcr-2026-0019
AB - Background: Breast invasive lobular carcinoma (ILC) with multiple organ metastases at initial diagnosis is rare. This study reports a case of ILC presenting with bone marrow and bone metastases at first diagnosis, in which the patient developed gastrointestinal metastases (GIMs) one year later, and reviews the relevant literature. Case Description: A 35-year-old female patient presented with a left breast mass accompanied by enlarged left axillary and cervical lymph nodes as well as thoracolumbar pain. Pathological biopsy confirmed the diagnosis of estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-low ILC, with metastases to the left axillary and cervical lymph nodes, bone marrow, and bone. The patient achieved tumor remission following treatment with endocrine therapy combined with a CDK4/6 inhibitor. One year later, she developed gastrointestinal symptoms such as nausea and vomiting. Pathological biopsy confirmed GIM from ILC, and the metastatic tumors harbored an ESR1 mutation (ESR1M) at p.Y537N. After treatment with the anti-HER2 antibody-drug conjugate (ADC) trastuzumab deruxtecan (T-DXd), disease control was achieved. Conclusions: Although ER-positive and HER2-low ILC can derive clinical benefit from endocrine therapy combined with a CDK4/6 inhibitor, the tumor may still undergo occult progression, such as ESR1M and GIM. This case highlights the importance of dynamic biomarker monitoring and repeat biopsy when occult progression is suspected. Anti-HER2 ADC therapy may provide disease control and clinical benefit in selected patients with HER2-low ILC after endocrine resistance.
SN - 2218-6778
ER -