Pediatric lacrimal sac non-keratinizing squamous cell carcinoma with DEK-AFF2 gene fusion: clinical and histopathological case report.

Inverted papillomas (IP) in children are extremely rare, benign epithelial growths known to recur. DEF-AFF2 squamous cell carcinoma (SCC), a newly identified, aggressive, and metastatic non-keratinizing SCC, can mimic IP. A 15-year-old male presented with recurrent episodes of left dacryocystitis and epiphora. His exam revealed left nasolacrimal duct obstruction, and an endonasal dacryocystorhinostomy was planned. Intraoperatively, there was a sudden prolapse of soft tissue after incising into the left lacrimal sac. Lesion biopsy initially revealed pathologic features consistent with inverted papilloma; however, RNA sequencing revealed a DEF-AFF2 fusion reclassifying it to SCC. Otolaryngology performed staged debulking followed by proton radiotherapy. There was no evidence of recurrence for 18 months. DEF-AFF2 SCC is a distinct, locally aggressive tumor with rare involvement of the lacrimal apparatus. Combined surgical and radiation therapy lead to adequate response. Accurate diagnosis requires a multidisciplinary approach due to its challenging and rare presentation, particularly in an atypical age group.