Margaret M. Mass, MD

Practice locations

Addresses where Margaret M. Mass is enrolled with Medicare (CMS data updated October 2, 2026).

• 509 Olive Way, 900 the Polyclinic DowntownSeattle, WA 98101 (206) 860‑4700

Group practices

Medicare enrollment lists Margaret M. Mass as a member of this group (CMS data updated October 2, 2026).

• The Polyclinic PLLC365 clinicians in the group

Specialties

• Family Practiceprimary

Find other Family Practice doctors in Washington →

Other family doctors in Seattle

Clinicians with the same Medicare primary specialty in Seattle, WA — not a recommendation.

• Kristen Kelly, MD
• Stephanie Gove-Yin, MD
• Patricia Egwuatu, DO
• Carla R. Ainsworth, MD
• Sara A. Fleming, MD
• Chinyere I. Obimba, MD
• Thomas I. Cherry, MD
• Jessica Goman, MD

All family doctors in Seattle →

Other clinicians in The Polyclinic PLLC

Medicare enrollment lists these clinicians in the same group practice — not a recommendation.

• William Curchin
• Eric W. Graham, MD
• Van Anh T. Ginger, MD
• Craig J. Pepin, MD
• Jae H. Sim, MD
• Anne Marie McLellan, DO

Clinician information

Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.

Sources

1. National Downloadable File (Doctors and Clinicians) — CMS, data updated October 2, 2026, retrieved October 29, 2026
2. NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
3. Medicare Care Compare — official Medicare tool to look up clinicians