There is a hard lump growing inside the armpit, which may be an enlarged lymph node, sebaceous cyst, lipoma, etc. The patient should consult a doctor in time to clarify the cause of the disease and then carry out treatment. 1. Enlarged lymph nodes: if the patient has infection foci near the armpit, it should be considered as inflammatory reaction enlargement, at this time, it should be treated for the primary cause of inflammation; if the patient has been diagnosed with malignant tumor and there is a lump in the armpit which is painful to press, it should be considered that it is caused by metastasis of the tumor’s lymph nodes. 2. Sebaceous cysts: when the sebaceous gland ducts in the armpit skin are blocked, the sebum will gradually silt up and form cysts, which can be manifested as painful lumps, if there is no symptom, there is no need to deal with it, and if there is a symptom, it can be surgically excised under the guidance of doctor. 3. Lipoma: benign tumor formed by proliferation of subcutaneous adipose tissue, the patient will have a local protrusion and a little painful lump, can be surgically removed under the guidance of the doctor.