Adenoid Cystic Carcinoma of the Sinonasal Cavity: A Case Report and Literature Review.

Introduction: Adenoid cystic carcinoma (ACC), a rare, aggressive malignancy of secretory epithelia, is often present with nonspecific symptoms, delaying diagnosis. Case Presentation: A 67-year-old male reported 10 months of nasal obstruction, mouth breathing, and sleep disturbances. The initial evaluation for foreign body obstruction revealed septal deviation and low-density sinonasal tissue on CT. MRI identified a 7 × 4.5 × 7 cm heterogeneous lesion invading nasal structures, paranasal sinuses, and nasopharynx with diffusion restriction. Tru-cut biopsy confirmed ACC via cribriform, tubular, and solid basaloid cell patterns, pseudocystic spaces, biphasic ductal-myoepithelial cells, and perineural invasion. Immunohistochemistry (CK7, CD117, p63, S100) supported the diagnosis, with tumor-free margins and no metastases. Multimodal therapy (30 VMAT sessions, 4 cisplatin-vinorelbine cycles) improved symptoms. Conclusion: This case illustrates ACC's diagnostic complexity, requiring advanced imaging and histopathology to exclude mimics. Despite indolent early progression, ACC's neurotropic spread and late-stage detection demand aggressive treatment. While surgery with adjuvant radiotherapy remains standard, the absence of metastases here underscores its variable behavior.