浸润性小叶癌（ILC）是浸润性乳腺癌的第二常见亚型，有时表现出异常的转移模式。其胃转移与原发性腺癌很难区分。本文报告了一例乳腺ILC的病例，其最初表现为胃转移。一名62岁的女性因胃出口梗阻次要于上消化道内窥镜和活检被诊断出胃肿瘤而被转诊进行18F-FDG PET/CT分期。基线18F-FDG PET/CT扫描显示大量腋窝淋巴结和胃转移，合并乳腺肿块，引起对原发乳腺癌的怀疑。鉴别原发性胃腺癌和转移性乳腺ILC非常重要，考虑到这两种诊断导致不同的治疗方案。因此，在临床实践中应考虑到这种情况在鉴别诊断中。© 2023 Society of Nuclear Medicine and Molecular Imaging.

Invasive lobular carcinoma (ILC) is the second most common subtype of invasive breast cancer and sometimes presents with an unusual metastatic pattern. Its gastric metastasis is difficult to differentiate from primary adenocarcinoma. This report presents a case of breast ILC for which the initial presentation was gastric metastasis. A 62-y-old woman presented with gastric outlet obstruction secondary to a gastric mass that had been diagnosed on upper gastrointestinal endoscopy and biopsy. The patient had been referred for 18F-FDG PET/CT for staging. The baseline 18F-FDG PET/CT scan demonstrated extensive axillary nodal and gastric metastases with a breast mass, which raised suspicion of a primary breast carcinoma. Distinguishing primary gastric adenocarcinoma from metastatic breast ILC is essential, considering that the 2 diagnoses lead to divergent treatments. Therefore, this entity needs to be considered in the differential diagnosis in clinical practice.© 2023 by the Society of Nuclear Medicine and Molecular Imaging.