Rare Airway Tumors in Dogs: Plasma Cell Tumors May Respond Well to Surgery

Canine Laryngotracheal Plasma Cell Tumors: Ten Cases and Literature Review

Kathleen R. Mulka, Deborah Gillette, Amy C. Durham, Elizabeth A. Mauldin

Background:
Extramedullary plasma cell tumors (EMPs) commonly arise in the skin, oral cavity, and gastrointestinal tract of dogs, but occurrence in the larynx and trachea is rare and not well characterized. The clinical behavior of laryngotracheal EMPs, particularly progression and recurrence rates, remains unclear. This study aimed to describe the histopathologic, immunohistochemical, and clinical features of laryngotracheal EMPs in dogs, supplemented by a review of the published literature.

Methods:
The anatomic pathology database at the University of Pennsylvania was searched for cases from January 2005 to April 2024. Ten cases of laryngeal or tracheal EMPs were identified. Histopathologic review and immunohistochemistry for CD3, CD79b, CD20, PAX5, and MUM-1 were performed. Clinical data were gathered from submission forms, medical records, and owner/veterinarian follow-up. A literature review of prior cases was also conducted for comparison.

Results:
All 10 dogs were male, aged 7–15 years, representing various breeds. Clinical signs included respiratory distress, cough, stridor, hypersalivation, and hemoptysis, although two masses were incidental findings. Histologically, tumors were composed of well- or moderately differentiated plasma cells, with variable mitotic activity and occasional amyloid deposition. Immunohistochemistry confirmed MUM-1 positivity in all cases; PAX5 and CD3 were negative, while CD20 and CD79b were variably positive. Surgical management (resection, debulking, or tracheostomy) led to no evidence of recurrence in 6 of 9 dogs over follow-up periods ranging from 2 months to 7 years. One case showed local progression after biopsy alone. Literature review of 8 additional cases revealed similar histopathologic findings and favorable outcomes post-surgical resection, although rare cases progressed to systemic disease.

Limitations:
This was a retrospective, small cohort study with variable clinical follow-up and incomplete staging. Histopathologic evaluation of margins was limited in many cases, and clonality was not consistently assessed with PARR. Only male dogs were included, limiting generalization across sexes.

Conclusions:
Laryngotracheal EMPs in dogs are rare but often manageable with surgical intervention, with good short- to medium-term prognosis in most cases. Immunohistochemistry is essential for definitive diagnosis. Further research is needed to better understand progression risks and the role of adjuvant therapy, especially in incompletely resected or recurrent cases.

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