‘Sweet syndrome’ associated with a primary nodal haemangiosarcoma in a dog

Abstract A 5‐year‐old, neutered, male Australian shepherd dog was presented with a week‐long history of fever, lethargy and hyporexia. Physical examination revealed an enlarged right retropharyngeal lymph node and multifocal, painful, non‐pruritic pustular skin lesions on the distal joints of all four limbs. Computed tomography identified a heterogeneously enhancing mass in the right retropharyngeal lymph node. Histopathology confirmed a nodal haemangiosarcoma, presumed to be the primary tumour in the absence of other detectable lesions. Skin biopsies revealed neutrophilic dermatitis consistent with Sweet syndrome. Surgical excision of the lymph node was followed by adjuvant chemotherapy with doxorubicin and concurrent glucocorticoids, leading to complete resolution of the skin lesions. Six months later, similar dermatological signs reappeared. A follow‐up computed tomography revealed metastases to the lymph nodes, spleen, liver and bones, along with a cutaneous relapse, reinforcing a paraneoplastic association. The dog was euthanased 470 days after initial diagnosis due to a pathological femoral fracture.