Case Report: Renal hemangiosarcoma in a free-ranging red fox (Vulpesvulpes).

This report describes the first documented case of primary renal hemangiosarcoma in a male red fox (Vulpes vulpes Linnaeus, 1758) admitted to the Wildlife Rescue Center "Federico II"-Veterinary Hospital of the Local Health Authority (ASL) Napoli 1 Centro in Naples, Italy. The fox, originating from a sparsely urbanized area, presented with progressive debilitation. Diagnostic imaging (ultrasound, radiography, CT) identified a mass in the right kidney. Citology suggested a malignant neoplasm, and histopathology confirmed hemangiosarcoma with multiple metastases to abdominal organs and to the heart. Necropsy revealed splenomegaly and a bladder lesion, while virological and bacteriological investigations excluded infectious diseases. The internal abdominal hemorrhages as consequence of tumor rupture were considered the cause of hypovolemic shock. This case underscores the value of advanced diagnostic techniques and systematic post-mortem investigations in wildlife medicine, contributing to the limited knowledge of neoplastic diseases in free-ranging foxes and highlighting the importance of wildlife health surveillance for ecological insight.