What is the limitation of the Kiupel scheme?

• A. It requires genetic testing
• B. 5–15% of dogs with Kiupel low-grade MCTs eventually die or are euthanized due to MCT-related disease, indicating inconsistency with clinical behavior
• C. It cannot be used for subcutaneous MCTs
• D. It is not reproducible across laboratories

Answer: (B)

The main idea here is that histologic grading helps predict prognosis but does not perfectly predict how an individual dog will actually behave clinically. The Kiupel scheme provides a simple two-tier system—low-grade and high-grade—that is designed to be more reproducible among pathologists than older schemes, and it generally correlates with outcomes.

However, its limitation is that some tumors labeled low-grade still behave aggressively. Data show that about 5–15% of dogs with Kiupel low-grade mast cell tumors die or are euthanized because of MCT-related disease. This means that histologic grade alone cannot fully capture the tumor’s biology or forecast what will happen in every patient. Other factors—such as tumor size, location, margins after excision, mitotic index, proliferative markers (like Ki-67), KIT receptor patterns, and metastatic status—also influence outcome and should be considered in prognosis and treatment planning.

The statement is not about genetic testing requirements, applicability to all MCTs without exception, or reproducibility issues across labs, which is why those options are not the best choice.