Esophageal carcinoma with ductal differentiation combined with multiple myeloma: a case report.

Esophageal carcinoma with ductal differentiation (ECDD) is a rare esophageal cancer (EC), characterized by distinctive morphological features, including bilayered duct-like structures and a biphenotypic immunophenotype. Multiple myeloma (MM) is a plasma cell neoplasm. The synchronous occurrence of these two entities is exceedingly rare. We report an 80-year-old male who presented with fatigue, anemia, and hypoalbuminemia. Endoscopic examination revealed a high-grade intraepithelial neoplasia of the esophagus. Following endoscopic submucosal dissection, pathological examination confirmed ECDD. Immunohistochemistry demonstrated that the inner layer cells of the duct-like structures were positive for CK7 and CAM5.2, while the outer layer cells were positive for p40 and p63. Concurrently, elevated serum globulin levels prompted further evaluation, leading to a diagnosis of MM. At 13 months postoperatively, no recurrence or metastasis of EC was observed, and the patient's MM remained stable. This case highlights that in elderly patients presenting with hematological abnormalities, the possibility of coexisting solid malignancy and plasma cell dyscrasia should be considered. ECDD has distinctive pathological features, and accurate recognition is critical to avoid misdiagnosis.