Melissa Mao, MD
Melissa Mao, MD is a Surgical Oncology Physician in Orange, CA, registered under NPI 1245594498. This provider registers 2 separate taxonomy codes, which usually means they practise across more than one recognised specialty.
Getting there
The practice address on file is 101 THE CITY DR S BLDG 23, Orange, CA 92868. We have not yet mapped what surrounds this office — parking, transit, and nearby pharmacies are added as our data collection reaches each location.
Credentials and Medicare
| Licence | State | Specialty |
|---|---|---|
| A167735 | CA | Surgical Oncology Physician primary |
| MD465525 | PA | Surgery Physician |
| A167735 | CA | Surgery Physician |
Licences are recorded in 2 states: CA, PA. Providers licensed in several states often practise near a state border or deliver telehealth across state lines.
- Status
- Approved
- Provider type
- Practitioner - General Surgery
- PAC ID
- 5294088563
Medicare enrolment is recorded as approved under the provider type Practitioner - General Surgery. This means the provider is enrolled to bill Medicare, though it does not tell you whether they are currently accepting new Medicare patients. Call the office to confirm.
Licensed in 2 states
This provider holds licences in 2 states: California and Pennsylvania. The practice address on file is in Orange, CA, but a licence in another state usually means they see patients there too — either at a second location or by telehealth. If the address above is far from you, it is worth calling to ask whether they practise closer to where you live.
- Licence
- A167735
- Specialty
- Surgical Oncology Physician
Licence numbers are self-reported to NPPES at registration. They do not confirm a licence is currently active, in good standing, or valid for the specialty shown — only the state board can tell you that, which is why we link to each one.
What Surgical Oncology covers
A surgical oncologist is a well-qualified surgeon who has obtained additional training and experience in the multidisciplinary approach to the prevention, diagnosis, treatment, and rehabilitation of cancer patients, and devotes a major portion of his or her professional practice to these activities and cancer research. NUCC Health Care Provider Taxonomy, code 2086X0206X
All registered taxonomy codes
This provider registers 3 taxonomy codes. The primary code is what appears on most claims; the others record additional recognised specialties.
| Code | Specialty | Licence | State | |
|---|---|---|---|---|
| 2086X0206X | Surgical Oncology Physician Surgical Oncology | A167735 | CA | primary |
| 208600000X | Surgery Physician | MD465525 | PA | |
| 208600000X | Surgery Physician | A167735 | CA |
The taxonomy records how the provider classifies their own practice. It does not confirm which conditions they currently treat, whether they are accepting new patients, or which insurance they take — call the office for that.
Full NPPES record
An NPI-1 identifies a single person. It stays with the clinician for life, even if they move practice or change state, which is why the address on file can lag behind where they actually work today.
| NPI | 1245594498 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Jul 2, 2012 |
| Last updated | Jun 2, 2025 |
| Status | Active |
| Sole proprietor | No |
| Credential | MD |
| Practice address |
101 THE CITY DR S BLDG 23 Orange, CA 92868 (714) 456-8000 |
| Mailing address |
200 S MANCHESTER AVE STE 300 Orange, CA 92868 |
Number check
How the check works, step by step
Every NPI carries a Luhn check digit — the same scheme used on credit cards. CMS prefixes the number with 80840 before computing it, which marks it as a US health identifier.
| Digit | 8 | 0 | 8 | 4 | 0 | 1 | 2 | 4 | 5 | 5 | 9 | 4 | 4 | 9 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 2 | 8 | 5 | 1 | 9 | 8 | 4 | 9 |
Sum = 72 · next multiple of 10 = 80 · check digit = 8 · actual last digit = 8
A valid check digit only means the number is well-formed. It does not mean the provider is licensed, active, or in good standing — those are separate questions answered by the sections above.