15 | Clinico-pathological features of superficial angiosarcomas: a retrospective study

Lorenzo Bellando¹, Chiara Anselmo², Giulia Orlando³, Leonardo Panarelli², Pietro Cosentino², Pietro Quaglino⁴, Franco Picciotto⁵, Simone Ribero⁴, Rebecca Senetta³ | ¹Pathology Unit, Città Della Salute e Della Scienza of Turin, University of Turin; ²Department of Medical Sciences, Pathology Unit, University of Turin; ³Department of Oncology, Pathology Unit, University of Turin; ⁴Department of Medical Sciences, Section of Dermatology, University of Turin; ⁵Department of Surgery, Dermatologic Surgery Section, Azienda Ospedaliera Universitaria Città della Salute e della Scienza, Turin, Italy.

Background: Angiosarcoma (AS) is a rare malignant vascular neoplasm, classified as either deep or superficial. Among superficial forms, cutaneous angiosarcoma (cAS) and radiation-induced angiosarcoma of the breast (RIAS) are the most frequent. Given the limited data available in the literature regarding clinico-pathological, immunophenotypic, and molecular prognostic or predictive parameters, this study aimed to investigate and validate novel clinical and morphological features related to diagnosis and disease progression.

Methods: A consecutive series of 21 cases of cAS and 16 of RIAS was retrospectively collected (2012-2024) from the pathology files of the Città della Salute e della Scienza of Turin. All cases were morphologically reviewed, with assessment of histopathological parameters such as Breslow thickness, Clark level, mitotic count, luminal formation (%), and grading. In addition, 10 atypical vascular lesions (AVL) of the breast and 20 cutaneous hemangiomas were selected as comparison groups. Immunohistochemistry for PRAME, p16, PD-L1, and MYC was performed using the Ventana BenchMark ULTRA.

Results: cAS were more frequent in males, with a median age of 75 years, and predominantly localized to the head and neck (62%). No morphological parameters showed a significant correlation with disease progression or survival status. However, cAS exhibited higher rates of brisk tumor-infiltrating lymphocytes (TILs), associated with improved outcome. PRAME expression was detected in only 11% of cAS, with no significant difference compared with hemangiomas. In RIAS, Breslow thickness correlated with disease progression (p=0.03). PRAME expression was more prevalent in RIAS compared with cAS (p=0.08) and significantly higher when comparing RIAS versus AVL (p=0.05). p16 expression was observed in >70% of tumor cells in most RIAS (9/14 cases), significantly higher than in cAS (p=0.03).

Conclusions: This study highlights Breslow thickness as a prognostic parameter in RIAS correlated with disease progression. PRAME immunohistochemistry may aid in the differential diagnosis between RIAS and AVL, particularly in incisional biopsies. The high prevalence of p16 expression in RIAS suggests a potential pathogenetic role.