Successful management of metachronous dual primary esophageal carcinomas: first report of consecutive adenoid cystic carcinoma and squamous cell carcinoma with exceptional treatment outcome-a case report.

BACKGROUND

Esophageal adenoid cystic carcinoma (ACC) is an exceptionally rare malignancy, and its association with second primary malignancies (SPMs) remains poorly characterized. This report presents the first documented case of metachronous esophageal squamous cell carcinoma (SCC) developing outside the radiation field following curative treatment of esophageal ACC.

CASE PRESENTATION: A 58-year-old male with a substantial smoking history presented with dysphagia in 2022. Diagnostic evaluation confirmed primary esophageal ACC (pT2N0M0, Stage IIA), exhibiting perineural invasion and a high proliferative index (Ki-67 80%). The patient underwent surgical resection followed by adjuvant radiotherapy (50 Gy/25 fractions) to the tumor bed. Postoperative radiotherapy was well tolerated, with only Grade 1 esophagitis and fatigue observed. Sixteen months later, during routine surveillance, a new cervical esophageal lesion was detected 5 cm proximal to the previous anastomotic site, well beyond the prior radiation field. Histopathological examination identified poorly differentiated SCC with distinct immunohistochemical characteristics (P40 diffuse+, Ki-67 30%). Complete remission was achieved following definitive chemoradiotherapy (60 Gy/28 fractions to PGTV, 54 Gy/28 fractions to PTV with concurrent S-1). At the most recent follow-up in March 2026, the patient remained disease-free.

CONCLUSION

This case illustrates that SPMs may arise outside irradiated regions after ACC treatment, excluding radiation-induced carcinogenesis. The findings emphasize the necessity of comprehensive endoscopic surveillance of the entire esophagus for early detection of secondary primaries in patients treated for esophageal ACC. Furthermore, the favorable therapeutic response demonstrates that curative-intent management remains feasible for metachronous malignancies when identified at an early stage.