Soreness in the armpit is common in clinical reasons such as strenuous exercise or activity and cystic hyperplasia of the breast, as follows: 1, strenuous exercise or activity: especially after the shoulder joint activity, resulting in local joint muscle strain formed by soreness, after 1-2 days of adequate rest, usually can get symptomatic relief and healing; 2, cystic hyperplasia of the breast: in clinical terms, it is more common in young and middle-aged women, because the appearance of Cystic hyperplasia of the breast causes reactive lymphadenitis in the lymph nodes of the armpit due to impaired reflux, and enlarged lymph nodes can be seen on ultrasound. Generally speaking, symptomatic treatment is usually needed for cystic hyperplasia of the breast, avoiding overexertion, taking sufficient rest, relaxing, and if necessary, taking oral Chinese medicines, such as Prosperity Pill, which can usually relieve and heal clinical symptoms.