16 year old female started on antibiotics for H Pylori Bacterial Infection in her stomach lining two days ago.  Complained last night of chest and stomach pain.  Woke up this morning with a painful lump on her left breast near her sternum -- sensitive to touch.  Severe pain to breathe deeply.
Hello, The most possible issue for a painful lump of the breast over the surface indicates infection in the sebaceous cyst or else and inside the breast tissue Fibroadenomas most likely. Clinical examination will be confirmatory to decide the final diagnosis. Hope I have answered your query. Let me know if I can assist you further.