Malignant mesenchymoma with widespread metastasis including bone marrow involvement in a dog

Abstract

A male castrated Golden Retriever was presented for evaluation of a large mass over the left shoulder extending to the lower part of the neck that had been present for an extended period of time, but had a recent history of rapid growth. Previous aspirates of the mass were consistent with a lipoma. The mass was surgically excised and was diagnosed as an extraskeletal osteosarcoma based on histopathology. After surgery, the dog was initiated on a chemotherapy protocol with carboplatin and metronomic cyclophosphamide. He became neutropenic, anemic, and thrombocytopenic 14 days after the carboplatin treatment was administered. The neutropenia resolved, but the anemia and thrombocytopenia progressed. A bone marrow aspirate revealed erythroid hypoplasia, myeloid hyperplasia with a predominance of early precursors, and a subset of cells that made up 20% of the total population that were reported as bizarre and unclassifiable. These cells were discrete in nature and were thought to be hematopoietic in origin. The dog was euthanized due to deterioration of the clinical condition. On postmortem examination, widespread metastasis involving the lungs, liver, kidney, heart, and bone marrow was found. Histopathology of the tumor lesions determined 2 distinct malignant populations of liposarcoma and osteosarcoma, consistent with malignant mesenchymoma. However, the possibility of 2 separate neoplastic processes cannot be definitively excluded. This is the first report of bone marrow metastasis of a malignant mesenchymoma in a dog.

The use of low‐dose metronomic chemotherapy in dogs—insight into a modern cancer field

“…Nonetheless, thus far, only 20 publications of clinical studies investigating metronomic drug delivery in small animals with cancer have been published. From these studies, 5 are case reports, and 15 provide data from a series of dogs . Only these last ones will be discussed in this work and can be found summarized in Table .…”

Metronomic chemotherapy: bridging theory to clinical application in canine and feline oncology

“…Although they are not discussed in this article given the nature of the study (case report or case series) and/or the number of animals included (less than 5), there are descriptions of the use of MC in the treatment of cutaneous angiomatosis ( 108 ), intradural-extramedullary haemangioblastoma ( 109 ), malignant Leydig cell tumour ( 110 ), malignant mesenchymoma ( 111 ), maxillofacial osteossarcoma ( 112 ), omentum myxosarcoma ( 113 ), prostatic leiomyosarcoma ( 114 ) and tonsillar carcinomas ( 115 ) in dogs and abdominal ( 116 ) and urinary bladder ( 117 ) hemangiosarcomas in cats.…”