Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum Sole proprietor

Michael Denis Masterson, M.D.

Medical Oncology Physician in Westlake Village, CA · enumerated 2006.

Data current as of Jul 13, 2026 · sourced from CMS NPPES

National Provider Identifier

1649240052

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Registry record

Entity type Individual (Type 1)

Name Michael Denis Masterson

Credential M.D.

Sex Male

Practice address Westlake Village, CA, 91361

Phone (805) 496-5153

Fax (805) 496-5202

Enumeration date Jan 26, 2006

Last updated in NPPES Feb 3, 2015

Street address withheld: NPPES sole-proprietor addresses can be home addresses. See our data policy.

Taxonomy & licenses

207RX0202X Medical Oncology Physician Allopathic & Osteopathic Physicians · License G27552 (CA) Primary

207RH0000X Hematology (Internal Medicine) Physician Allopathic & Osteopathic Physicians · License G27552 (CA) Secondary

MD · Doctor of Medicine: A physician who completed medical school (allopathic medicine), residency training, and state licensure. About the MD credential

Other identifiers

Identifier	Type	State	Issuer
WG27552A	Other	CA	MEDICARE PTAN
G27552	Other	CA	MEDICAL LICENSE

What is an NPI number?

A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes, even if the provider moves or changes specialty.

Read the full guide → Validate an NPI →

Frequently asked questions

How do I verify Michael Masterson's NPI record?

Cross-check NPI 1649240052 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.

Is NPI 1649240052 active?

Yes, as of the latest NPPES snapshot, NPI 1649240052 is active (record last updated 2015-02-03).

Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2015-02-03.