Malignant mesenchymoma of the heart base in a dog with infiltration of the pericardium and metastasis to the lung

A case of hepatic leiomyosarcoma with osteosarcomatous differentiation (malignant mesenchymoma) in a dog

A rare spontaneous hepatic leiomyosarcoma with osteosarcomatous differentiation was observed in a female beagle dog and its morphological and immunohistochemical characteristics were examined. Upon necropsy, an endoceliac mass originating from the liver was detected, which was composed of hematoid fluid-filled cysts and white to grayish solid tissue. There were no macroscopic findings in other organ systems. Histopathologically, the hepatic mass consisted of two different mesenchymal components. One form was spindle cells arranged in interlacing fascicles immunohistochemically positive for smooth muscle actin (SMA) and smoothelin, indicating leiomyosarcomatous differentiation. The other form was composed of short spindle cells positive for S-100 and was producing various amounts of eosinophilic osteoid and trabecula-like matrices positive for osteocalcin, indicating osteosarcomatous differentiation. In addition, invasive growth in the hepatic parenchyma and cell atypia were observed. Based on these findings, the mass was diagnosed as hepatic leiomyosarcoma with osteosarcomatous differentiation (malignant mesenchymoma), which might be derived from undifferentiated mesenchymal cells.

Left ventricular cardiac myxoma and sudden death in a dog

Background

Myxoma is a very rare benign cardiac tumor in dogs. This is the first description of a cardiac myxoma originating from the left ventricular outflow tract, presumably causing sudden death.

Case presentation

A previously healthy 12-year-old male West Highland white terrier was found dead during its 1-week stay in a kennel. The dog was known to have a cardiac murmur. On necropsy, a pedunculated neoplasia was found attached to the interventricular aspect of the left ventricular outflow tract, resulting in almost complete obstruction of the aorta. As this was the only abnormality identified, the tumor was considered as the cause of sudden death. Histopathologic findings were compatible with a myxoma.

Conclusions

Benign intraluminal tumors of the heart are very rare in dogs, but may have fatal consequences. Echocardiography could have revealed the cause of the cardiac murmur of this previously asymptomatic dog. Surgical removal could have been possible, as the tumor was pedunculated.

Acute undifferentiated leukaemia in a dog

BACKGROUND

Acute undifferentiated leukaemia (AUL) is considered a separate entity in the context of acute leukaemias. AUL is extremely rare in both humans and dogs, has a rapid clinical course and does not respond to treatment. It is characterised by the presence of blast cells within the bone marrow and/or peripheral blood at levels ≥ 20% and even up to 100% of all nucleated cells. Blast cells are unable to be differentiated on morphological, cytochemical and phenotypic criteria into myeloid or lymphoid lineages because of their immaturity and/or atypia.

CASE REPORT

An 8-year-old German Shepherd dog was referred for depression, asthenia, mild anaemia, thrombocytopenia and marked leucocytosis. Abdominal ultrasound showed hepatomegaly, splenomegaly, bilateral nephromegaly and enlargement of mesenteric lymph nodes. Echocardiography revealed biventricular hypertrophy with abnormal tissue density of the myocardium. Blood and bone marrow smears were composed of 95% unclassifiable and/or atypical blast cells and signs of dysplasia of the erythroid and thrombocytic/megakaryocytic lineages were present. Blast cells were negative for all cytochemical stains used and flow cytometry of peripheral blood revealed 85% of total leucocytes consisting of small-to-medium-sized cells, negative for all lymphoid and myeloid markers except CD45 and CD34. After necropsy, cytology and histology revealed that blast cells had diffusely infiltrated all tissues examined. Both erythroid and megakaryocytic extramedullary haemopoiesis was also detected in the spleen, lymph nodes and liver. All immunohistochemical stains used were negative.

CONCLUSION

On the basis of all the results, a diagnosis of acute leukaemia involving a very primitive haematopoietic precursor was made.