Background Most molecular association studies in papillary thyroid carcinoma (PTC) have focused on single-gene events or selected co-mutations. Whether a pragmatic multigene-based grouping is associated with preoperative ultrasonographic features and postoperative pathological features remains unclear.Methods We retrospectively included patients who underwent thyroidectomy for pathologically confirmed PTC at a single center between April and December 2025. Multigene testing was performed on postoperative FFPE specimens. Using a postoperative FFPE-based grouping approach defined by multigene results, patients with wild-type results or isolated BRAF V600E were grouped as Low-MRG, and all others as High-MRG. Univariable analyses used Fisher's exact test and the Wilcoxon rank-sum test. Size-adjusted models included maximum tumor diameter on preoperative ultrasonography and used Firth penalized-likelihood logistic regression or ordinary least-squares linear regression. Benjamini–Hochberg false discovery rate correction was applied.Results Seventy-nine patients were included (High-MRG, n = 15; Low-MRG, n = 64). In unadjusted analyses, High-MRG was associated with larger maximum tumor diameter on ultrasonography (median 2.50 vs. 1.30 cm; q value = 0.011), lower aspect ratio (0.74 vs. 1.01; q value = 0.031), suspicious cervical lymph nodes on ultrasonography (86.7% vs. 46.9%; OR = 7.37; q value = 0.034), aggressive histological subtypes (53.3% vs. 14.1%; OR = 6.98; q value = 0.027), and advanced T stage (60.0% vs. 20.3%; OR = 5.88; q value = 0.027). After adjustment for maximum tumor diameter, associations with suspicious cervical lymph nodes on ultrasonography, aggressive histological subtypes, and advanced T stage were attenuated. A greater total number of positive lymph nodes remained associated with High-MRG after size adjustment (β = 7.065; q value = 0.019).Conclusions In this exploratory postoperative FFPE-based grouping approach, High-MRG was associated with adverse preoperative ultrasonographic and postoperative pathological features, but most associations were attenuated after adjustment for tumor size. The most stable size-adjusted finding was a greater total number of positive lymph nodes. Further evaluation in larger multicenter cohorts, ideally using preoperative FNA specimens, is needed.