Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Dr. Mark L. Sobczak, MD

Radiation Oncology Physician in Philadelphia, PA · enumerated 2005.

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

National Provider Identifier

1164422523

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Registry record

Entity type Individual (Type 1)

Name Dr. Mark L. Sobczak

Credential MD

Sex Male

Practice address 333 Cottman Ave, Philadelphia, PA, 19111

Phone (215) 728-2581

Fax (215) 214-4038

Enumeration date Jul 28, 2005

Last updated in NPPES Jun 6, 2018

Taxonomy & licenses

2085R0001X Radiation Oncology Physician Allopathic & Osteopathic Physicians · License D0060531 (MD) Secondary

2085R0001X Radiation Oncology Physician Allopathic & Osteopathic Physicians · License 0101046483 (VA) Secondary

2085R0001X Radiation Oncology Physician Allopathic & Osteopathic Physicians · License C1-0007087 (DE) Secondary

2085R0001X Radiation Oncology Physician Allopathic & Osteopathic Physicians · License 36651 (KY) Secondary

2085R0001X Radiation Oncology Physician Allopathic & Osteopathic Physicians · License MD-045641-L (PA) Primary

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

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.

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Frequently asked questions

Is NPI 1164422523 active?

Yes, as of the latest NPPES snapshot, NPI 1164422523 is active (record last updated 2018-06-06).

How do I verify Mark Sobczak's NPI record?

Cross-check NPI 1164422523 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2018-06-06.