Bilateral invasive lobular breast carcinoma with synchronous gastric metastasis and orbital pseudotumor mimicking metastasis: a case report

BACKGROUND: Invasive Lobular Carcinoma forms 10-15% of all breast cancers. ILC is usually ER positive and HER-negative and characterized by Loss of E-cadherin expression. These features contribute to the infiltrative growth pattern to GI tract, peritoneum, and orbit. GI metastasis represents 1% of cases. Hence, an additional orbital involvement is very uncommon. CASE PRESENTATION: We present a 54-year-old postmenopausal female with a positive family history of breast cancer who presented with bilateral upper outer quadrant breast masses. Biopsy showed bilateral grade II ILC, positive for ER and progesterone receptor (PR), and negative for HER-2. Staging CT revealed bilateral breast lesions with axillary lymphadenopathy, gastric and colonic wall thickening, ascites, and pelvi-ureteric junction constriction. There were no metastases to the lung or liver. Brain MRI showed a right intraconal orbital lesion that was initially suspected of being metastasis. The patient received 12 cycles of paclitaxel (80 mg/m²) followed by tamoxifen and goserelin maintenance. Due to recurrent vomiting and right-sided ptosis, imaging and ophthalmologic evaluation were repeated, identifying the orbital lesion as an inflammatory pseudotumor that responded to corticosteroids. Bone scans showed no osseous deposits. Neurologic evaluation revealed axonal motor polyneuropathy attributed to chemotherapy, which was managed with plasma exchange. The patient maintained stable disease until loss to follow-up in early 2023. CONCLUSION: This case demonstrates a rare gastric metastasis in bilateral ILC in addition to a diagnostic challenge of differentiating orbital metastasis from pseudotumor.