Background

Angiomyofibroblastoma (AMFB) is an uncommon benign mesenchymal tumor of the female genital tract, rarely reported in humans and exceptionally rare in animals. Typical human cases arise in the vulva, vagina, or cervix and are usually small, well-demarcated lesions. Prior to this report, only one canine case had been documented in veterinary literature, and a uterine AMFB had never been described in a cat. Because AMFB contains numerous thin-walled blood vessels, large masses may pose significant perioperative risks if not accurately diagnosed. This case report details the first feline uterine AMFB and underscores the importance of proper diagnostic and surgical planning.

Methods

An 18-year-old intact female domestic shorthair cat presenting with abdominal distension underwent clinical assessment including hematologic and biochemical analyses, radiography, and abdominal ultrasonography. Following suspicion of uterine neoplasia or pyometra, an emergency hysterectomy was performed. The excised uterus was evaluated grossly and processed for histopathology, Masson’s trichrome staining, and immunohistochemistry using α-SMA and desmin antibodies. Standard antigen retrieval, blocking, and chromogenic detection techniques were employed.

Results

Imaging revealed a markedly enlarged uterus displacing abdominal organs. Laboratory abnormalities included elevated proBNP, lactate, and leukocytosis. The cat experienced cardiac arrest intraoperatively following ligation of the ovarian branch of the uterine artery. Grossly, the uterus was firm, 10 × 6 cm, and mottled with hemorrhagic areas. Histopathology showed well-differentiated spindle cells arranged in alternating cellularity patterns within abundant fibromyxoid stroma. Numerous blood vessels with perivascular hyalinization were present, with no mitotic figures or inflammatory infiltrates. Neoplastic cells expressed α-SMA diffusely and desmin focally. These features supported a diagnosis of angiomyofibroblastoma. The exceptionally large size likely contributed to circulatory compromise and intraoperative hemodynamic collapse.

Limitations

As a single case report, generalization is limited. No preoperative biopsy was performed, preventing confirmation prior to surgery. Perioperative monitoring details were limited, and the cause of intraoperative arrest cannot be fully proven but is inferred from tumor characteristics. Long-term outcome was not obtainable due to the cat’s death during surgery.

Conclusions

This report documents the first known case of uterine AMFB in a cat. Although AMFB is considered benign, large tumors may severely impair circulation due to mass effect and high vascular load, posing substantial operative risk. Accurate preoperative diagnosis and preparation—including anticipation of significant intraoperative blood loss and cardiovascular instability—are critical. AMFB should be included in the differential diagnosis of feline uterine mesenchymal tumors to guide safer perioperative management.

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