A complex histopathological challenge: suspicion of an osteoblastoma-like osteosarcoma arising from the second thoracic vertebra in a cat

Abstract

Background Reports of osteoblastic tumours are limited to a few case reports in veterinary medicine. Osteoblastoma-like osteosarcoma has been accepted by the World Health Organization as an intermediate form between an osteosarcoma and osteoblastoma. This type of tumour indicates an osteosarcoma, that may resemble osteoblastoma clinically, histologically, and radiologically and have the capability for metastasis. Osteoblastoma-like osteosarcoma has not been described in veterinary medicine so far. Case presentation An eight-year old cat was presented due to progressive ataxia and paraparesis of the pelvic limbs. Imaging confirmed a well-defined, extradural mass originating from the spinous process of the second thoracic vertebra (T2) leading to severe compression of the spinal cord. Decompressive cytoreduction was achieved by removal of the mass after dorsal laminectomy of T1. After recovering from an acute worsening 3.5 weeks after surgery, the cat had an improved neurological status and the dorsal compression was resolved at follow-up 8 months later. A focal contrast enhancing lesion was still evident at the base of T2 spinous process and lung metastasis was additionally suspected. Based on histopathological, radiographic, and clinical features, an “osteoblastoma-like osteosarcoma” was suspected. Conclusions To the best of our knowledge, this is the first description of this tumour in veterinary medicine. In addition, this case report highlights the difficulty in the diagnosis and definition of osseous neoplasia in cats and provides a literature review.

Demographics, clinical findings and diagnoses of cranial thoracic myelopathies (T1–T6 vertebrae) in cats

“…1,2,4 Intervertebral disc herniation is reported to be more common in the lumbar region of cats, 5,6 and reports of disorders affecting the thoracic spinal cord in cats are currently limited to case reports and small case series, such as articular process hypertrophy resulting in vertebral canal stenosis, [7][8][9][10] vertebral hyperostosis, 11 intervertebral disc protrusion (IVDP), 12,13 subarachnoid diverticulum 14 and different types of neoplasia. 15,16 A recent publication described the signalment, clinical presentation and differential diagnoses of cranial thoracic myelopathies (between the T1 and T6 vertebrae) in dogs; 17 however, to the authors' knowledge, there is still a lack of information on myelopathies affecting this region in cats. This information could be useful, as it may allow a clinician to advise the owner of an affected cat regarding the most likely differential diagnoses after suspicion of a lesion in this region, which could then be used to formulate a focused and appropriate diagnostic plan.…”

“… 1 , 2 , 4 Intervertebral disc herniation is reported to be more common in the lumbar region of cats, 5 , 6 and reports of disorders affecting the thoracic spinal cord in cats are currently limited to case reports and small case series, such as articular process hypertrophy resulting in vertebral canal stenosis, 7 – 10 vertebral hyperostosis, 11 intervertebral disc protrusion (IVDP), 12 , 13 subarachnoid diverticulum 14 and different types of neoplasia. 15 , 16 …”

Vertebral Osteosarcoma in Two Cats—Diagnosis, Treatment, and Outcome

“…Compared with its canine counterpart, feline osteosarcoma (FO) is infrequently diagnosed in veterinary medicine [1][2][3][4][5][6]. FO affecting the axial skeleton, or feline vertebral osteosarcoma (FVO), is only described in detail in a few veterinary publications [7][8][9][10][11]. These publications have provided important information regarding possible outcomes of surgical and medical treatment.…”

“…Based on the literature, aggressive surgical treatment seems to be the most effective treatment for all types of FO, irrespective of additional treatment such as chemotherapy [1][2][3][4][5][6][7][8][9][10][11]. Mean survival times are reported to be shorter for FVO compared to appendicular FO [1,2].…”

“…Local recurrence is reported after cytoreductive surgical treatment [11]. Still, there are recent case reports that document favorable long-term outcomes for the surgical treatment (with additional chemotherapy) of FVO [7][8][9][10].…”