MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests at least 80% of the fund’s net assets in issuers with medium market capitalizations. MFS generally defines medium market capitalization issuers as issuers with market capitalizations similar to those of issuers included in the Russell Midcap® Index over the last 13 months at the time of purchase. As of November 30, 2025, the range of the market capitalizations of the issuers in the Russell Midcap® Index was between between approximately $956.3 million and $115.7 billion.

Effective June 10, 2026, the paragraph directly above is restated in its entirety with the following paragraph:

MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests at least 80% of the fund’s net assets in growth companies with medium market capitalizations. MFS defines medium market capitalization companies as issuers that (i) have market capitalizations within the capitalization range of the Russell Midcap® Index over the past 12 months based on the current composition of the index and/or are (ii) classified as a medium capitalization company by an independent third party financial data provider. The market capitalization range of companies considered to have medium capitalizations based on the above criteria will change over time depending on market conditions. For illustrative purposes, as of November 30, 2025, the range of the market capitalizations of the issuers in the Russell Midcap® Index was between approximately $956.3 million and $115.7 billion, and the fund’s average weighted market capitalization as of that date was $39.3 billion. Growth companies are companies that MFS believes have above average potential with respect to the rate and duration of earnings growth compared to other companies. MFS considers a number of factors when determining a company’s growth potential, including whether (i) the issuer is included in an index that is representative of growth companies; (ii) the issuer is classified as a growth company by an independent third party; and/or (iii) the issuer exhibits the characteristics of a growth company, considering metrics such as historical and/or projected growth rates relative to the applicable equity market. Growth companies tend to have stock prices that are high relative to their earnings, dividends, book value, or other financial measures.

MFS normally invests the fund’s assets primarily in equity securities. Equity securities include common stocks, depositary receipts, and other securities that represent an ownership interest (or right to acquire an ownership interest) in a company or other issuer.

Effective June 10, 2026, the sentence directly below is deleted in its entirety.

MFS focuses on investing the fund’s assets in the stocks of companies it believes have above average potential with respect to the rate and duration of earnings growth compared to other companies (growth companies).

MFS may invest the fund’s assets in foreign securities.

MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers. Quantitative screening tools that systematically evaluate issuers may also be considered.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.