case_images: PMC11795834_01
case_images: Computed tomography image showing a retroperitoneal mass near the lesser curvature of the stomach, measuring 32 mm x 31 mm.
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case_images: Enhanced computed tomography (CT) of the chest and abdomen revealed a retroperitoneal mass near the lesser curvature of the stomach, with indistinct boundaries between the stomach and pancreas and uneven enhancement patterns (Fig. 1).
case_images: T2-weighted magnetic resonance imaging showing a space-occupying lesion measuring approximately 46 mm x 34 mm in the posterior peritoneum between the pancreas and the lesser curvature of the stomach.
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case_images: An enhanced scan revealed enhancement at the solid site (Fig. 2).
case_images: Histopathological findings indicating pure, poorly-differentiated squamous cell carcinoma, with abundant cytoplasmic keratin pearls and intercellular bridges. (Hematoxylin and eosin staining, original magnification x100).
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case_images: Histopathological assessment revealed poorly differentiated pancreatic carcinoma with stomach invasion and regional lymph node metastasis, consistent with SCC (tumor size, approximately 5.5 cm x 4.0 cm x 4.0 cm; Fig. 3).
case_images: Tumor cells testing positive for CK5/6 expression (CK5/6 immunohistochemistry, x100).
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case_images: Immunohistochemical analysis revealed that the malignant cells expressed CK5/6 (Fig. 4), p40 (Fig. 5), CK19, HER2 (2+), Ki-67 (+, 80 %), and Brg-1.
case_images: Timeline of patient's course of treatment.
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case_images: Genetic test results indicated the amplification of the tyrosine kinase receptor 2 (ERBB2) gene, prompting treatment with trastuzumab in combination with tegafur suppositories (Fig. 6).