Mass. Gen. Laws ch. 180, § 4
A corporation may be formed for any one or more of the following purposes:
(n) for establishing a not-for-profit association of employers as authorized by section twenty-five E of chapter one hundred and fifty-two, including such not-for-profit associations of employers organized as nonprofit corporations.
If a corporation is formed under this chapter for the purpose of rendering one or more professional services as defined in chapter one hundred and fifty-six A, the relationship between the corporation or an employee thereof rendering professional service and the person receiving such service shall be the same as if such corporation or employee rendered such service to said person as an individual practitioner, including any liability arising out of the rendering of such service.