# Atypical Intestinal Metastases from Invasive Lobular Carcinoma of the Breast: Two Surgical Cases Mimicking Primary Gastrointestinal Tumors

## TL;DR

This paper presents two cases where breast cancer spread to the intestines, mimicking primary gut tumors, highlighting the importance of accurate diagnosis using special tests.

## Contribution

The paper contributes two rare clinical cases of intestinal metastases from invasive lobular breast cancer, emphasizing diagnostic challenges and the role of immunohistochemistry.

## Key findings

- Intestinal metastases from ILC can mimic primary GI tumors and present with bowel stenosis.
- Immunohistochemical profiling is essential for distinguishing ILC metastases from primary GI tumors.
- Surgical resection aids in diagnosis and symptom relief, though it may not improve survival.

## Abstract

Gastrointestinal metastasis arising from invasive lobular carcinoma (ILC) of the breast is a rare but clinically significant manifestation. Unlike invasive ductal carcinoma, ILC has a higher propensity to metastasize into the gastrointestinal (GI) tract, often presenting with non-specific symptoms and mimicking primary GI tumors. Its accurate diagnosis requires a high index of suspicion and immunohistochemical (IHC) confirmation. Herein, we report 2 cases of intestinal metastases from ILC presenting with bowel stenosis.

Case 1 involved a 45-year-old woman with no known primary malignancy, who presented with duodenal and small bowel strictures. CT revealed narrowing of the small intestine, along with multiple sclerotic bone lesions. Surgical resection was performed, following which histopathological examination revealed ILC with a characteristic IHC profile (CK7+, CK20–, GATA3+, CDX2–, E-cadherin–). Retrospective breast imaging and biopsy confirmed a diagnosis of primary ILC. Case 2 involved a 57-year-old woman with a known history of luminal-type ILC. At 56 months postoperatively, bone metastasis was detected and PET-CT revealed uptake in the sigmoid colon. Furthermore, colonoscopy demonstrated stricture with no visible mucosal lesions. Surgical resection was subsequently performed, following which IHC confirmed metastatic ILC with a receptor status (ER+, PgR+, HER2–) matching that of the primary tumor.

These cases demonstrate the diagnostic challenges posed by GI metastases arising from ILC, particularly due to submucosal infiltration and lack of endoscopic findings. IHC plays a critical role in differentiating these lesions from primary GI tumors. Although surgical resection may not prolong survival, it is valuable for symptomatic relief and for establishing a definitive diagnosis. Surgeons should be aware of the risk of ILC metastasizing into the GI tract. In patients presenting with atypical intestinal stenosis—particularly those with a history of ILC—metastasis should be considered. In such cases, IHC-guided diagnosis is essential.