Abstract
Background:
Primary intraosseous squamous cell carcinoma (PIOSCC) is a rare and aggressive malignancy that originates within the bone, reported in both humans and animals. While squamous cell carcinoma (SCC) is the most common oral tumor in cats, PIOSCC is an uncommon variant with distinct clinical and pathological features.

Case Description:
A 10-year-old spayed female Domestic Longhair cat presented with a progressively enlarging mass at the rostral mandible. Over six weeks, the cat exhibited clinical signs including inappetence, excessive salivation, and pain. Diagnostic evaluations comprised hematology, serum biochemistry, head radiographs, fine needle aspiration, and histopathology. A diagnosis of solid-type PIOSCC was confirmed post-mortem, based on histopathological and immunohistochemical findings.

Conclusion:
This case represents the first documented instance of solid-type PIOSCC in a cat in Jordan. It highlights the importance of early recognition and accurate diagnosis of this rare, locally invasive tumor. Given the poor prognosis, humane euthanasia was chosen as the most appropriate course of action.

Key words: Feline squamous carcinoma; Intraosseous tumor; Mandibular mass; Immunohistochemistry.