Daily Practice

The International Classification of Diseases, 10th Edition (ICD-10)

ICD-10 Replaced ICD-9 on October 1, 2015

The ICD-10 code set replaced the ICD-9 code set on October 1, 2015. Claims submitted using ICD-9 codes after this date will be rejected. In July 2015, the Centers for Medicare and Medicaid Services (CMS) announced that it will allow a certain degree of leniency in submitting ICD-10 codes during the first year of implementation. As long as an ICD-10 code is submitted using a valid code from the correct family, the ICD-10 claim will not be denied, even if it is not coded to the highest level of specificity. Medicare Administrative Contractors, Recovery Audit Contractors, Zone Program Integrity Contractors and Supplemental Medical Review Contractors will adhere to this policy.

CMS will apply the same specificity standard to the Physician Quality Reporting System (PQRS), Value Based Modifier (VBM) and Meaningful Use (MU) programs for program year 2015. Medicare clinical quality data review contractors will not penalize physicians or other Eligible Professionals (EPs) as long as they submit the ICD-10 code from the correct family of codes. CMS also created an ICD-10 Ombudsman that will work as a liaison between physicians and CMS’ regional offices. For more information on these policies, visit the CMS website.

The transition to ICD-10-CM does not affect CPT® coding for outpatient procedures and physician services. These services should continue to be reported using CPT and Healthcare Procedure Coding System (HCPCS) codes.

The ICD-10 code set varies significantly from ICD-9. The chart below provides a snapshot of the differences between the two code sets. The Basics of the ICD-10 Code Set.

Comparison: ICD-9 versus ICD-10




Number of codes

17,000 (approximately)

150,000 (approximately)

Code structure – Length

3-5 characters

3-7 characters

Code structure – Type of Digits

Digit 1 – alpha or numeric

Digits 2-5 – numeric

Digit 1 – alpha

Digits 2-3 – numeric

Digits 4-7 – alpha or numeric

Capacity to add codes

Limited space for adding new codes

Space for adding new codes

Level of detail

Lacks detail

Very specific


Lacks laterality

Has laterality (i.e., right vs. left)


ICD-10-CM disease classification includes significantly more health-related conditions and greater specificity. The following revisions are new to ICD-10-CM:

  • Information relevant to ambulatory and managed care encounters.
  • Expanded injury codes.
  • Creation of combination diagnosis/symptom codes to reduce the number of codes needed to fully describe a condition.
  • The addition of sixth and seventh character classifications.
  • Incorporation of common fourth and fifth character classifications.
  • Classifications specific to laterality.
  • Classification refinement for increased data granularity.


  • C40.32: Malignant neoplasm of short bones of left lower limb.
  • C50.311: Malignant neoplasm of lower-inner quadrant of right female breast.
  • The first digit is always alpha. (Neoplasms will always begin with either “C” or “D.”)
  • The second and third digits are always numeric.
  • The decimal is always after the third digit.
  • The fourth through seventh digits are either alpha or numeric.


A Closer Look at Neoplasm Diagnostic Codes 
While the transition to ICD-10 is a significant change, ASTRO’s review of the neoplasm diagnostic codes suggests that the transition from ICD-9 to ICD-10 appears to be relatively straightforward for our subset of codes. The chart below provides some example mappings from ICD-9 to ICD-10 relevant to radiation oncology.

ICD-9 Code

ICD-9 Descriptor

ICD-10 Code

ICD-10 Descriptor




Malignant neoplasm of liver, primary


Other specified carcinomas of liver


Malignant neoplasm of liver, primary, unspecified as to type


Malignant neoplasm of trachea


Malignant neoplasm of trachea


Malignant melanoma of skin of eyelid, including canthus


Melanoma in situ of eyelid, including canthus, unspecified side


Melanoma in situ of right eyelid, including canthus


Melanoma in situ of left eyelid, including canthus


Malignant melanoma of eyelid, including canthus, unspecified side


Malignant melanoma of right eyelid, including canthus


Malignant melanoma of left eyelid, including canthus


Malignant neoplasm of prostate


Malignant neoplasm of prostate