Abstract
Background:
Feline inflammatory mammary carcinoma (FIMC) is a rare, aggressive malignancy characterized by rapid progression and a poor prognosis. FIMC is often not clinically suspected prior to histopathological confirmation because of its low incidence. With its recent inclusion in the World Health Organization classification, awareness of secondary forms of FIMC is becoming increasingly important.

Case Description:
A 13-year-old spayed female mixed-breed cat with a 1-cm mammary tumor between the right third and fourth glands, previously diagnosed as common mammary carcinoma by cytology 3 months earlier, was referred for severe pain associated with rapid tumor progression and skin erythema. The lesion had enlarged to 1.5 cm with multiple 1–2-mm nodules and diffuse erythema extending from the lower abdomen to the labia. Several distinct 5-mm nodules, clearly separated from the mammary chain, were also identified in the right dorsal lumbar skin. All accessible tumors (bilateral third and fourth mammary glands and right lumbar lesions, each with 2-cm margins) were palliatively resected to alleviate pain and obtain a definitive diagnosis. Histopathology revealed mammary carcinoma with neoplastic emboli in dermal lymphatics; when interpreted in conjunction with the clinical history, this finding was consistent with secondary FIMC. Postoperatively, the cat’s pain score decreased from 18 to 3 within 24 h, and appetite improved. Sequential treatment with lapatinib, toceranib, and firocoxib, followed by metronomic chlorambucil for pulmonary metastases, achieved local disease stabilization. The cat remained pain-free for 185 days before death from uremia.

Conclusion:
This case represents one of the first reports of secondary FIMC developing from a pre-existing mammary tumor without prior surgery. Because FIMC has only recently been included in the World Health Organization classification, it is frequently unrecognized before histopathological examination. This case highlights the diagnostic challenges associated with secondary FIMC and demonstrates that multimodal palliative therapy can help cats with advanced FIMC maintain their quality of life.

Key words: Cat; Chlorambucil; Feline inflammatory mammary carcinoma; Lapatinib; Toceranib.