Can the Patnaik grading scheme be used for subcutaneous mast cell tumors?

• A. Not enough data
• B. Yes
• C. No
• D. Only for certain grades

Answer: (C)

The Patnaik grading scheme is a historical three-tier system developed for canine cutaneous mast cell tumors, and its histologic criteria were validated for tumors in the dermis. Subcutaneous mast cell tumors arise in deeper soft tissues where their histologic architecture and biological behavior differ from skin lesions, so the same criteria don’t reliably predict prognosis in those locations. Using Patnaik to subcutaneous MCT can misclassify aggressiveness and misguide management. In modern practice, subcutaneous MCTs are assessed with grading systems validated for non-dermal sites (and often with contemporary two-tier schemes) alongside other prognostic histologic and clinical factors, rather than applying Patnaik.