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A 74-year-old woman was diagnosed with stage Ⅳ breast carcinoma at our
hospital in 2016 and is currently undergoing chemotherapy. Chest and
abdominal computed tomography (CT) showed axillary lymph node metastases
and osteolytic bone metastases in the skull and the spine. There were no
obvious metastasis in the gastrointestinal tract. In December 2022, she
visited her previous doctor for treatment of anorexia. An
esophagogastroduodenoscopy (EGD) conducted by her previous doctor
revealed sclerosis and poor extension of the gastric wall, which
indicated that it was a type 4 advanced gastric cancer (AGC; Figure 1).
EGD was performed again at our facility and 8 biopsies were taken. All
these biopsies showed poorly differentiated adenocarcinoma, indicating
that the metastasis originated from the breast carcinoma. Furthermore,
to confirm this diagnosis, the expression levels of hormone receptors in
cancer tissues were examined by immunohistochemical (IHC) analyses. The
proportions of estrogen- and progesterone-receptor-positive cells were
60 and 5 % (Allred’s total scores: 6 and 4), respectively. Human
epidermal growth factor receptor 2 (HER2) score was estimated at 2+
(equivocal), and FISH analysis revealed no HER2 gene amplification.
Ki-67 (MIB-1) labeling index was 25 % in the hot spot (so-called
luminal B-like subtype). E-cadherin was mostly negative, or weakly
positive, GATA binding protein 3 were diffusely positive, gross cystic
disease fluid protein 15 were variously positive, and mammaglobin was
focally positive. In addition, cytokeratin 7 was positive, whereas
cytokeratin 20 was negative (Figures 2 and 3). Based on these
pathological findings, the diagnosis of gastric metastasis derived from
invasive lobular carcinoma was confirmed.
Currently, endocrine therapy for breast carcinoma contributes
significantly to mortality reduction and recurrence
control.1 However, the endoscopic and pathologic
findings of gastric metastases derived from breast carcinomas are often
mistaken to be the findings of type 4 AGC, thereby delaying correct
diagnosis and therapeutic intervention. Gastric metastases derived from
breast carcinomas should be especially kept in mind in cases of women
with a history of breast carcinoma. Accurate endoscopic diagnosis,
EGD-biopsies, and pathological examinations, including IHC, are
important for differentiating between gastric metastases derived from
breast carcinomas and type 4 AGCs. In addition to highlighting the
importance of IHC, we have focused on another interesting point in the
present study: owing to EGD-biopsies, cases of gastric metastases
derived from breast carcinomas are easier to diagnose than cases of type
4 AGCs. In our current case, cancer tissue was abundant in all eight
biopsy specimens. In the case of type 4 AGC, the diagnosis of
adenocarcinoma using EGD-biopsy specimens is not so common, as clinical
reports have shown that the proportion of definitive diagnoses made on
the basis of EGD-biopsy results is approximately 50
%.2, 3 In the future, examining the proportion of
diagnosis by EGD-biopsies in both may contribute to the rapid diagnosis
of gastric metastases derived from breast carcinomas.