Tumors of the lacrimal sac are a rare entity. Malignancies are often associated with a high mortality rate. Lacrimal sac tumors often present as lacrimal duct stenosis with dacryocystitis and are often only diagnosed after an intraoperative biopsy. The aim of this study was a retrospective analysis of all cases with lacrimal sac tumors, which presented with a lacrimal duct stenosis at this medical center in the past 10 years.All patients who were treated by external dacryocystorhinostomy (DCR) at the University Medical Center Münster during the period January 2009-December 2018 were retrospectively analyzed for the presence of a lacrimal sac tumor. Symptoms, clinical and histopathological findings, diagnostic and therapeutic procedures as well as long-term follow-up were analyzed.A total number of 878 patients underwent an external DCR at the University Medical Center Münster during the study period. Of these patients 13 were diagnosed with a lacrimal sac tumor and included 9 malignant lymphomas, 2 squamous cell carcinomas, 1 oncocytic adenoma and 1 transitional cell papilloma.Neoplasms of the lacrimal sac can masquerade as lacrimal duct stenosis or dacryocystitis and must be considered as a differential diagnosis in cases with an atypical clinical course. A lacrimal sac biopsy during an (external) DCR with subsequent histopathological examination is strongly recommended in such cases.