Figure 4 Histopathological and immunohistochemical features of jejunal metastasis from primary lung adenocarcinoma. (A) Hematoxylin and eosin (H&E)-stained section demonstrating infiltrative adenocarcinoma involving the ileal wall beneath an intact intestinal mucosa. The tumor is composed of irregular infiltrating glands embedded within a desmoplastic stroma. (B) Higher-power H&E photomicrograph showing malignant glandular and focal cribriform architecture lined by atypical epithelial cells with enlarged hyperchromatic nuclei, nuclear pleomorphism, and prominent nucleoli, consistent with metastatic adenocarcinoma. (C) Immunohistochemical staining demonstrating diffuse strong cytoplasmic and membranous positivity for cytokeratin 7 in the neoplastic cells, supporting a pulmonary origin. (D) Immunohistochemical staining showing diffuse cytoplasmic positivity for napsin A, a sensitive marker of pulmonary adenocarcinoma, confirming the pulmonary origin of the mtastatic lesion.