Histopathological, histochemical and immunoistochemical study on a rare case of granulocytic sarcoma in a dog

Granulocytic sarcoma is a malignant extramedullary solid tumor, composed of granulocytic precursor cells at various levels of differentiation. Three differentiation levels are considered: blastic, immature, and differentiated, and cases with unusual morphology. Nowadays the aid of more and more highly developed techniques allows to differentiate the various histotypes. We report a case of a 5 year-old female Schnautzer dog, died after a serious dyspnoea. During the autopsy the veterinary found several neoplasias in the lungs. It has been found a very large white-greyish mediastinal neoplasia, stuck at the trachea and several more in the parenchyma. Several samples were fixed in formalin, embedded in paraffin and exposed to histochemistry staining (H.E., Giemsa), cytochemistry (Naphthol-AS-D-Chloroacetate), and immunohistochemistry (anti-CD3, -CD79a, -CD45, -MPO, -CD45Ro, -CD34, -CD20, -CD68, -CD15, -CD30, -CD117, -CD235a, -Factor VIII, -elastase and anti-Pan-cytocheratine). Neoplasia, poorly circumscribed, was composed by a large number of neutrophil granulocytes with different degrees of differentiation, including elements of myeloid lineage. Cells were positive to MPO and focal to Naphtol-As-D-Chloroacetate and were negative to all the others antisera, allowing us to exclude lymphomas, small cells carcinomas, and tumors of monocytic and erythroid origin. By these characteristics we could diagnose a rare case of neutrophilic granulocytic sarcoma, of immature type progressing to mature form.