Neoplasms with splenic involvement in dogs at necropsy: Macroscopic presentation patterns in 262 cases.

Splenic neoplasm is frequently diagnosed in dogs and can present as nodules or splenomegaly. This retrospective study aimed to characterize the gross features of splenic neoplasm in dogs at necropsy in order to recognize possible presentation patterns for each diagnosis. In a 10.5-year period, 1,187 dogs underwent necropsy with a confirmed diagnosis of neoplasia, of which 262 had splenic neoplasm. Three dogs had two distinct concurrent tumours, totalling 265 splenic neoplasms. Of these, non-angiogenic tumours were diagnosed in 217 cases (81.9 %) and angiogenic neoplasms were diagnosed in 48 cases (18.1 %). Most non-angiogenic neoplasms were metastatic (50.2 %), mainly epithelial and round cell in origin, with multifocal, red to white nodules, followed by multicentric (31.8 %) and primary (18 %) tumours. Lymphoma was the main multicentric neoplasm, often with splenomegaly associated with micronodular or nodular pattern. Most primary tumours were stromal sarcomas, which often exhibited focal nodules. Haemangiosarcoma was the most common angiogenic neoplasm, frequently with multifocal red nodules in multiple organs. Angiogenic tumours and primary non-angiogenic tumours were significantly larger than multicentric and metastatic tumours, but no statistical difference was observed. These findings indicate that although gross overlap among splenic tumour types persists, certain macroscopic patterns, such as focal nodules in stromal sarcomas, multifocal nodules in haemangiosarcomas and larger size of angiogenic and primary non-angiogenic neoplasia, may help guide initial differential diagnoses.