Case report highlights occult carcinoma behind multifocal bone lesions
Bottom line
Version 1
A new case report in Veterinary Sciences describes an unusual and fast-moving presentation of carcinoma of unknown primary origin, or CUP, in a 15-year-old spayed female Jindo-mix dog. The dog was referred for rapidly progressive tetralimb lameness and inability to stand after two weeks of worsening forelimb lameness. Advanced imaging identified aggressive multifocal skeletal lesions, and the report says the case ultimately ended in fatal systemic thrombosis, underscoring how CUP can present as diffuse bone disease rather than a clearly localized primary tumor. The authors argue that this pattern can closely mimic primary bone neoplasia or multicentric lymphoma, making diagnosis especially difficult. (pmc.ncbi.nlm.nih.gov)
Why it matters: For veterinary professionals, the case is a reminder that metastatic carcinoma should stay on the differential list when an older dog presents with rapidly progressive, multifocal osteolytic or mixed skeletal lesions, even when no primary tumor is found. Prior veterinary literature suggests skeletal metastasis is often the first clinical sign of carcinoma in dogs, and in many cases the primary site remains unidentified despite extensive workup or even necropsy. That matters for case planning, because biopsy and staging can shift the conversation away from presumptive primary bone cancer and toward systemic disease, prognosis, pain control, and thrombotic risk. Carcinomas are also among the tumor types most associated with hypercoagulability and thrombosis in dogs, adding another layer to monitoring and supportive care. (pubmed.ncbi.nlm.nih.gov)
What to watch: Watch for whether this report prompts more discussion around coagulation assessment and broader metastatic workups in dogs with atypical polyostotic bone lesions. (frontiersin.org)
Key facts
- Article type
- Case report
- Journal
- Veterinary Sciences
- Patient
- 15-year-old spayed female Jindo-mix dog
- Presenting signs
- Rapidly progressive tetralimb lameness and inability to stand
- History
- Two weeks of worsening forelimb lameness
- Imaging findings
- Aggressive multifocal osteolytic and osteoproliferative skeletal lesions
- Outcome
- Fatal systemic thrombosis
- Diagnostic challenge
- Can mimic primary bone neoplasia or multicentric lymphoma
Version 2
A newly published case report in Veterinary Sciences highlights a rare and diagnostically difficult presentation of carcinoma of unknown primary origin in a dog: rapidly progressive multifocal skeletal lesions accompanied by fatal systemic thrombosis. According to the report summary, the patient was a 15-year-old spayed female Jindo-mix dog referred for tetralimb lameness and inability to stand after a two-week history of worsening forelimb lameness. The authors say the disease pattern closely resembled other better-known differentials, including primary bone neoplasia and multicentric lymphoma. (pmc.ncbi.nlm.nih.gov)
That diagnostic confusion has precedent in the veterinary literature. A classic retrospective study of 19 dogs found that skeletal metastasis was the initial clinical manifestation of malignancy in most cases reviewed, with lesions occurring most often in the axial skeleton and proximal long bones. In that cohort, the primary tumor could not be determined in 58% of dogs, and even complete postmortem evaluation did not always identify it. A later retrospective study of 21 dogs with metastatic cancer of unknown primary found a median survival of just 30 days, with bone among the most common metastatic sites and the primary site still unidentified in 95.2% of cases. (pubmed.ncbi.nlm.nih.gov)
The new report adds to that limited body of evidence by focusing on a particularly aggressive skeletal presentation. Based on the source description, computed tomography showed aggressive multifocal osteolytic and osteoproliferative lesions, and the case progressed to fatal systemic thrombosis. Even without the full article text available through search, that combination is clinically notable: multifocal bone lesions in an older dog can point clinicians toward osteosarcoma, round-cell neoplasia, metastatic disease, or selected infectious differentials, and this case reinforces that occult metastatic carcinoma belongs on that list. (aaha.org)
Other published canine case reports support the same caution. A 2019 report described squamous cell carcinoma of unknown primary origin presenting with bone metastasis, while another report documented skeletal metastasis from transitional cell carcinoma before the primary urinary tract tumor was confirmed. A separate case report published in 2023 also emphasized that metastatic CUP remains sparsely described in dogs and should still be considered as a differential diagnosis despite its rarity. Taken together, those reports suggest this is not a common presentation, but it is recurrent enough to deserve attention in oncology, internal medicine, radiology, and pathology workflows. (pmc.ncbi.nlm.nih.gov)
The thrombosis piece may be just as important as the bone findings. A recent review in Frontiers in Veterinary Science says carcinomas are among the canine tumor types most strongly linked to hypercoagulability, thrombosis, and overt disseminated intravascular coagulation, echoing patterns long recognized in human oncology. That makes the fatal systemic thrombosis in this case more than an isolated complication; it fits a broader biologic pattern that may be underrecognized in dogs with advanced carcinoma. The AAHA 2026 oncology guidelines also reinforce the value of full staging and minimum database assessment when cancer is suspected, particularly when imaging suggests internal or osseous involvement. (frontiersin.org)
Why it matters: For veterinary professionals, this case sharpens two practical points. First, rapidly progressive multifocal skeletal disease in an older dog should trigger a broad differential diagnosis and tissue-based confirmation where feasible, rather than an automatic assumption of primary bone tumor. Second, if metastatic carcinoma is on the table, clinicians may need to think earlier about systemic complications, including thromboembolic disease, prognosis, and palliative planning. For pet parents, the presenting complaint may look like orthopedic pain or sudden mobility decline, but for the care team it can signal disseminated malignancy with very limited survival time. (pubmed.ncbi.nlm.nih.gov)
What to watch: The next question is whether more case aggregation follows. Because CUP in dogs is still sparsely reported, each additional case can help clarify which imaging patterns, biopsy strategies, immunohistochemical panels, and coagulation findings are most useful, and whether thrombosis surveillance should play a larger role in managing dogs with suspected metastatic carcinoma and multifocal bone lesions. (pmc.ncbi.nlm.nih.gov)