What could cause swollen lymph nodes in his chest along with shortness of breath and slight chest pain?

Lymph nodes can become swollen from infection, inflammatory conditions, an abscess, or cancer. Other causes of enlarged lymph nodes are rare. By far, the most common cause of swollen lymph nodes is infection.

When swelling appears suddenly and is painful, it is usually caused by injury or an infection. Enlargement that comes on gradually and painlessly may, in some cases, result from cancer or a tumor.

It best to see a doctor for a correct diagnosis.