Private equity firm sells ownership stake in Solis Mammography

A private equity firm has quietly exited its ownership stake in Solis Mammography. 

Chicago-based Madison Dearborn Partners first acquired the breast imaging group in August 2018 from fellow PE firm Audax. A leading provider of mammograms, biopsies and other related women’s health services, Solis has since then more than tripled in size, going from about 50 locations to more than 150 as of last year. 

MDP subsequently sold its stake in the Addison, Texas-based imaging firm to Towerbrook Capital in May 2025, a Solis representative told Radiology Business Tuesday. Neither buyer nor seller has posted an official announcement online in the eight months that have followed the deal. 

Solis Mammography and Madison Dearborn Partners declined to comment on the transaction, while Towerbrook did not respond to Radiology Business requests for comment. MDP’s webpage, however, confirms it has exited its ownership stake in the company. 

“With expert breast radiologists, next-generation technologies, and a personalized, woman-focused approach, Solis Mammography offers a superior mammogram experience,” New York-based Towerbrook says on its healthcare portfolio page, which has been updated to include Solis. 

Founded in 2000, Towerbrook is primarily focused on transforming service businesses across Europe and North America, also operating offices in London. Besides healthcare, it holds assets in business and financial services and consumer products. Towerbrook’s other healthcare investments include revenue cycle management firm R1 RCM, staffing outfit the Acacium Group, physical therapy business PT Solutions, and outpatient surgery provider Regent Surgical, among others. Altogether, the private equity firm has made over 115 investments with $26 billion in assets under management.

Towerbrook Co-CEO Karim Saddi briefly mentioned the deal in a recent company report, noting that it’s part of their Delta Fund of investments, “further expanding the positive impact of our capital.” In another recent report, Cain Brothers’ Jeff Danesis, managing director specializing in radiology and other physician services, notes that Towerbrook’s acquisition of Solis is part of a “surge in sector deal activity” across the private capital market. He labeled the buy as a “large sponsor-backed recapitalization,” similar to TPG’s 2023 investment in MedQuest Associates, another imaging provider. 

Solis Mammography, meanwhile, was founded in 1986 and first partnered with Audax PE in February 2015. In the three years leading to the 2018 Madison Dearborn Partners deal, the two companies worked together to open 28 new centers in addition to completing five add-on acquisitions and inking two joint ventures. Solis grew during the hold period from 27 locations up to 55 at the time of the 2018 exit and developed a pipeline of over 150 acquisition targets across the country. 

Same store revenue grew nearly 11% during Audax’s hold period amid increased volume and adoption of 3D mammography, according to the PE firm’s website. In partnership with Solis, it supported the platform’s rapid growth, also aiding in executive hires including a CFO, COO, CDO and CIO. 

“We had a highly successful partnership with Solis Mammography and shared their vision to become a leading provider of mammography services,” Adam Abramson, managing director of the Audax Group, said in a post published on Audax’s website. “Together, we invested in the company’s infrastructure and executed numerous acquisitions and joint ventures to support profitable, long-term growth.”

Solis Mammography has continued its rapid growth trajectory after the May 2025 sale to Towerbrook. Acquisitions since then have include the St. Louis Breast Center in Ballwin, Missouri, in October; the Knoxville Comprehensive Breast Center in Tennessee in December; and the Women's Center for Radiology in Orlando, Florida, earlier this month. Under Towerbrook ownership, Solis also hired Emily Sedgwick, MD, MBA, as its new chief medical officer in November. The company now operates an estimated 163 centers spanning 24 major markets as of Friday, a representative says.