Hepatic Epithelioid Hemangioendothelioma in a Dog

Simple Summary Hemangioendothelioma is an uncommon neoplasm that affects both humans and animals. Its clinical course is unclear. This report describes the first case of hepatic epithelioid hemangioendothelioma in a dog. The clinical and microscopic characteristics of this neoplasm overlap with those described in humans; therefore, this report can be informative as a spontaneous animal model but, at the same time, also useful for veterinary progress in diagnostic orientation and therapeutic treatment.Abstract A 5-year-old spayed female Breton dog was referred for a thyroid nodule. A total body CT scan evidenced multifocal hepatic nodules. Cytological liver samples were hemodiluted and non-diagnostic. Following a thyroidectomy, the histology was consistent with a follicular-compact thyroid carcinoma. On laparoscopy, most hepatic lobes had multifocal dark-red nodules that were biopsied for histology. Microscopically, the hepatic parenchyma in the nodules was substituted by blood channels lined by bland spindle cells but adjacent to epithelioid neoplastic cells, single or in clusters, embedded in a moderate amount of edematous collagen matrix. These cells had optically empty cytoplasmic space, occasionally containing erythrocytes (microlumina). Spindle and epithelioid cells expressed membranous-to-cytoplasmic CD31 and FVIII-RA consistent with endothelial origin. Based on morphology and immunolabelling, a hemangioendothelioma with epithelioid differentiation was diagnosed. Lesions in the liver were initially stable, showing progression with time. The dog was alive with no systemic clinical signs 36 months after laparoscopy.