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ICD-9-CM procedure code (retired)

20.42 — Radical mastoidectomy

ICD-9-CM was replaced by ICD-10 on October 1, 2015. These are the ICD-10-PCS equivalents from the CMS General Equivalence Mappings.

About ICD-9-CM 20.42

20.42 is an ICD-9-CM procedure code for radical mastoidectomy. ICD-9-CM was retired for U.S. claims on October 1, 2015, when ICD-10-PCS took over.

The CMS General Equivalence Mappings translate it to 6 ICD-10-PCS codes, such as 09TB0ZZ (Resection of Right Mastoid Sinus, Open Approach), 09TB4ZZ (Resection of Right Mastoid Sinus, Percutaneous Endoscopic Approach) and 09TB8ZZ (Resection of Right Mastoid Sinus, Via Natural or Artificial Opening Endoscopic). All of these are approximate matches, so review the record to pick the right one.

ICD-10-PCS equivalents

Common questions about 20.42

What is the ICD-10 code for ICD-9 20.42?

The GEMs map 20.42 to ICD-10-PCS 09TB0ZZ, 09TB4ZZ, 09TB8ZZ, 09TC0ZZ, 09TC4ZZ and 09TC8ZZ.

GEMs are a translation aid, not a substitute for coding from the record. The 2027 ICD-10 code set has changed since the last GEMs release in 2018. Page updated September 29, 2026.