Background/Objectives: Nasopharyngeal angiofibroma (NA) is generally benign, but recurrent disease and rare malignant transformation remain clinically relevant beyond adolescence. We examined adult clinical presentations, records of malignant transformation, and age-related differences in stage distribution. Methods: We retrospectively reviewed 289 surgically treated patients from January 2006 through June 2026. Radkowski stage distributions were compared between patients aged > 30 and ≤30 years using exact tests. Detailed clinical records were reviewed for 16 adults, and whole-genome sequencing (WGS) annotation summaries were examined for one tumor–blood pair. Results: Twenty-five patients (8.7%) were older than 30 years; stage was available for 287 patients. In the detailed adult subgroup, a prior pathology-slide record described focal malignant transformation with a Ki-67 index of approximately 50% in one recurrent tumor. Two other patients had database transformation entries without accompanying pathological documentation. Four recurrences and three deaths were recorded, all in stage IIIB disease. Three men had colorectal or rectal cancer histories. Low-, intermediate-, and advanced-stage tumors accounted for 36.0%, 36.0%, and 28.0% of adult cases, compared with 17.6%, 57.3%, and 25.2% of younger cases (p = 0.0493). The genomic annotations showed a C>A-predominant substitution spectrum. Conclusions: Adult NA included recurrent stage IIIB disease and a documented record of focal malignant transformation. Stage distributions differed between age groups. These clinical observations support pathological reassessment of recurrent tumors. The single-case genomic findings remain descriptive annotations.