A woman’s vague pain in the upper left side of her left breast near her armpit may be the discomfort caused by breast enlargement, and this kind of bad symptom may also occur when she suffers from mastitis and pleurisy. 1. Mammal hyperplasia: Mammal hyperplasia may cause a vague pain in the upper left side of the left breast near the armpit, usually the patient will have breast pain, lumps and other symptoms, the pain will spread to the breast around, touching the local area there will be obvious nodules, and some patients will have nipple overflow. 2. Mastitis: A vague pain in the upper left side of the left breast near the armpit can also be caused by mastitis, with this kind of disease there will be breast pain, swelling, redness and swelling and other symptoms, and some patients will be accompanied by fever. 3. pleurisy: pleurisy can also lead to such adverse symptoms, the patient will appear chest tightness, chest pain and other discomforts, may also cause coughing, coughing, with the development of the disease, may cause breathlessness, or even respiratory difficulties, will also cause different degrees of fever. There are paratesticular breasts in the premenstrual period will also appear in the armpit part of the hidden paroxysm of pain, the emergence of such adverse symptoms need to consult a doctor in a timely manner, identify the cause of the disease, under the guidance of the doctor’s advice to choose the appropriate treatment, to avoid delaying the condition.