Utility of fine-needle aspiration in diagnosing secondary solid gastrointestinal malignancy.

INTRODUCTION: Secondary solid malignancies involving the gastrointestinal tract (GIT) are uncommon and often present as subepithelial or deeply seated lesions, limiting the diagnostic yield of endoscopic mucosal biopsy. The utility of fine-needle aspiration (FNA) in setting remains underexplored. MATERIALS AND METHODS: We retrospectively reviewed cases of secondary solid GIT malignancies diagnosed by FNA at a single institution from 2000 to 2025. Clinical, radiologic, and pathologic data were analyzed, and FNA performance was compared with endoscopic mucosal biopsy when both were performed. RESULTS: Fifty-nine patients (mean age, 64 years) were identified with the stomach as the most frequently involved site (49%). Breast carcinoma and pancreatobiliary tract carcinomas were the most common primary malignancy. Most patients had widespread metastatic disease and poor overall survival. Imaging demonstrated either intraluminal subepithelial nodules/masses or diffusely infiltrative wall thickening. Endoscopic mucosal biopsy was performed in 28 patients but yielded concordant results in only 29%, corresponding to a false-negative rate of 71%. Among 205 nondiagnostic or negative GIT FNA specimens with follow-up tissue sampling, 2 cases were subsequently diagnosed with metastatic carcinoma. Similarly, metastatic carcinoma was identified on follow-up in 2 of 55 atypical FNA cases. Using follow-up tissue diagnosis as the reference standard, FNA achieved a sensitivity of 93.7% and specificity of 100%. CONCLUSIONS: Secondary GIT tumors represent advanced systemic disease with poor prognosis. FNA is a reliable, minimally invasive diagnostic modality, particularly for deeply seated lesions where conventional endoscopic biopsy has a high false-negative rate.