Abstract
Errors that occur in anatomic pathology influence the treatment strategy of patients with malignancy. There are four general types of error with three subtypes in the category of defective interpretation. The first subtype is a false-negative diagnosis or undercall of the extent or severity of the lesion, the second is a false-positive diagnosis, and the third is misclassification. We herein report a 65-year-old female patient with malignant gastrointestinal stromal tumor that was diagnosed after reevaluation of the lesion at our hospital - and treated with proximal gastrectomy - after initial diagnosis as malignant B-cell lymphoma on esophagogastroduodenoscopy biopsy of a small gastric fundic mass and subsequent treatment with six cycles of CHOP chemotherapy with aggravation of the mass at another hospital.