With lucrative fees for doctors, little oversight, and much disagreement about who needs stents in their heart arteries, it was perhaps inevitable that malpractice allegations of unnecessary surgery would explode into hundreds of lawsuits against a single cardiologist in Baltimore.

But now a new report from the U.S. Senate Finance Committee, which oversees the federal Medicare program, says the Maryland cases against Dr. Mark Midei may be only the tip of a very large iceberg.