Mesothelioma, unspecified

This code identifies a malignant neoplasm arising from the mesothelial cells lining the pleura, peritoneum, or pericardium, when the specific anatomical site is not documented. It represents a rare and aggressive cancer often associated with asbestos exposure.

Use this code when the medical record clearly states a diagnosis of mesothelioma but does not specify the primary site (e.g., pleural, peritoneal, pericardial). Documentation should confirm the presence of mesothelioma without further anatomical detail.

• Avoid using this code if the specific site of the mesothelioma is known; instead, use a more specific code from the C45 category (e.g., C45.0 for pleural mesothelioma).
• Always review pathology reports and imaging studies for definitive site identification before defaulting to "unspecified."
• Consider sequencing this code as the primary diagnosis when it is the reason for the encounter or treatment.