Extramedullary hematopoiesis in a case of benign mixed mammary tumor in a female dog: cytological and histopathological assessment

Abstract

BackgroudExtramedullary hematopoiesis (EMH) is defined as the presence of hematopoietic stem cells such as erythroid and myeloid lineage plus megakaryocytes in extramedullary sites like liver, spleen and lymph nodes and is usually associated with either bone marrow or hematological disorders. Mammary EMH is a rare condition either in human and veterinary medicine and can be associated with benign mixed mammary tumors, similarly to that described in this case.Case presentationHematopoietic stem cells were found in a benign mixed mammary tumor of a 7-year-old female mongrel dog that presents a nodule in the left inguinal mammary gland. The patient did not have any hematological abnormalities. Cytological evaluation demonstrated two distinct cell populations, composed of either epithelial or mesenchymal cells, sometimes associated with a fibrillar acidophilic matrix, apart from megakaryocytes, osteoclasts, metarubricytes, prorubricytes, rubricytes, rubriblasts, promyelocytes, myeloblasts. Histological examination confirmed the presence of an active hematopoietic bone marrow within the bone tissue of a benign mammary mixed tumor.ConclusionsEMH is a rare condition described in veterinary medicine that can be associated with mammary mixed tumors. It's detection can be associated with several neoplastic and non-neoplastic mammary lesions, i.e. osteosarcomas, mixed tumors and bone metaplasia.

Extramedullary Hematopoiesis: A New Look at the Underlying Stem Cell Niche, Theories of Development, and Occurrence in Animals

“…In humans, EMH has been reported in association with cerebellar hemangioblastoma, astrocytoma, hemangioma, hepatoblastoma, leiomyoma, pilomatricoma, hepatic angiosarcoma, endometrial carcinoma, meningioma, hepatic adenoma, spindle cell lipoma, liposarcoma, myofibroblastic tumors, and renal tumors. 78 EMH has been reported in up to 42% of hemangiosarcomas in dogs, 6 in a benign mixed mammary tumor in a dog, 30 and in histiocytic sarcomas in mice and dogs. 57,71 We have observed EMH in cytologic specimens from histiocytic sarcomas in dogs (Fig.…”

Consensus regarding the diagnosis, prognosis and treatment of canine mammary tumors: benign mixed tumors, carcinomas in mixed tumors and carcinosarcomas

“…Bone formation occurs via the endochondral ossification of pre-existing cartilage formed by the differentiation of myoepithelial cells or the intramembranous ossification of the connective tissue of the stroma (27). The presence of bone marrow with haematopoietic tissue and intermingled adipose tissue are observed in some cases (2,28).…”

Myeloid metaplasia in canine mixed mammary tumors: occurrence and characterization

“…Recently, Grandi et al (2010) reported a case of extramedullary hematopoiesis in a benign mixed mammary tumor of a dog. Cytological analysis, prior to surgical resection of the tumor, showed hematopoietic young, mature and precursors cells, such as rubriblasts, myeloblasts, promyelocytes, megakaryocytes, prorubricytes, rubricytes, metarubricytes, erythrocytes, and a discrete quantity of osteoclasts.…”