Subcutaneous undifferentiated pleomorphic sarcoma is more aggressive than pleomorphic dermal sarcoma: Prognosis from a Danish nationwide registry-based cohort

Introduction
Subcutaneous undifferentiated pleomorphic sarcoma (scUPS) has not previously been described separately from pleomorphic dermal sarcoma (PDS), and consequently the prognosis for patients with scUPS is unknown.
Materials and methods
In this nationwide cohort study, we identified all patients in Denmark diagnosed with scUPS or PDS between 2002 and 2022. The outcomes were 5-year local recurrence, loco-regional and distant metastasis, and overall survival.
Results
We included 271 patients, 131 with scUPS and 140 with PDS. Patients with scUPS exhibited higher 5-year risks than patients with PDS in terms of the overall risk of metastasis (19 % vs. 7 %, p = 0.006) and distant metastasis only (12 % vs. 2 %, p = 0.004). The 5-year overall survival for patients with scUPS was 50 %, compared to 67 % for patients with PDS (p = 0.004).
Conclusion
Our findings indicate that patients with scUPS have a significantly worse prognosis than patients with PDS, with a higher overall risk of metastasis and a prolonged metastatic risk. This suggests a more extended follow-up program focusing on the detection of distant metastasis for patients with scUPS, whereas the follow-up of patients with PDS can be limited to clinical controls.