2008 ICD-9-CM Volume 1 Diagnosis Codes Home > Neoplasms 140-239 > Benign Neoplasms 210-229 > Benign Neoplasm Of Respiratory And Intrathoracic Organs 212.* > 2008 ICD-9-CM Diagnosis 212.5 Benign neoplasm of mediastinum  On October 1, 2008 the 2009 ICD-9-CM codes came into effect. Therefore, this code may be out of date. The 2009 version of ICD-9-CM 212.5 can be accessed here. Abnormal growth of the cells of the tissues contained within the mediastinum (e.g., thymus) without evidence of malignancy. 212.5 is a specific code that can be used to specify a diagnosis View the ICD-9-CM Volume 1 212.* hierarchy ICD9Data's sister site ProcedureCodes.com launches with the 2008/09 CPT® codes - read more on the ICD9Data.com blog.