Rapid malignant transformation of sinonasal inverted papilloma: comparative case series highlighting clinical challenges and management complexity

Abstract Background Sinonasal inverted papilloma (SNIP) is a benign epithelial tumor with an unpredictable risk of malignant transformation. Despite reported transformation rates of up to 17%, risk stratification remains largely biopsy-dependent, which may underestimate aggressive behavior due to sampling limitations. Case presentation We report three cases of SNIP with malignant transformation exhibiting divergent clinical courses. The first patient presented with fulminant carcinoma at initial diagnosis, rapidly progressing despite radical surgery. In the second case, the patient developed malignant transformation after 15 years of recurrent disease and multiple surgeries. The third patient had abrupt malignant progression within weeks following a prolonged benign course, despite initially reassuring imaging and histology. In all cases, early histology was non-predictive, while serial imaging demonstrated aggressive progression preceding or discordant with pathological confirmation. These cases highlight the limitations of static, biopsy-centric risk assessment in SNIP. Malignant transformation may be focal, or rapidly progressive, rendering single-time-point histology insufficient. Serial imaging and emerging molecular markers offer complementary insights for risk stratification. We propose a dynamic, multimodal, risk-adaptive framework to guide surveillance and escalation of management. Conclusion Benign histology alone does not exclude malignant potential in SNIP. Dynamic, behaviour-driven risk assessment incorporating serial imaging is essential for timely detection and management.