This is a spontaneous report from a contactable consumer (Patient). A 50-year-old female patient received first dose of BNT162B2 (PFIZER-BIONTECH COVID-19 mRNA VACCINE; solution for injection, Lot Number: unknown), via intramuscularly, in left arm on 05Mar2021 12:00 (at the age of 50-year-old) as a dose 1, single for COVID-19 immunization. The patient medical history included diagnosed allergies, compromised immune status, respiratory illness, genetic / chromosomal abnormalities, endocrine abnormalities ((including diabetes), obesity and hemochromatosis diagnosed two years ago. The concomitant medication of the patient was not reported. Family medical history none.Patient had not taken any vaccination prior within 4 weeks. On 05Mar2021 the patient experienced right breast milk ducts inflamed. On 06Mar2021 patient had rash on right breast. On 08Mar2021 patient reported that rash was going down chest, on both breast and front of neck. Patient reported that she had a very strange side effect. Patient right breast, in the milk ducts, are inflamed. Patient was in 50 and not breast feeding, and they should not be active. Patient stated that breast is inflamed, have a rash and are sensitive to touch. This occurred a few days after patient got the shot. The rash was going down the front of chest, on both breast and up to front of neck. Her right breast was engorged and painful. Patient stayed and was very painful and did not start to go down until Sunday evening.Then, it had a large rash around it, but patient could feel the lump. Patient went to her breast doctor and she said it was a cluster of milk ducts, so that area around it was large and inflamed and had a large circle red rash around them. Patient took Aleve and it helped. No details for the Aleve provided. By Monday, Patient breast improved and patient could still feel the ducts, but the overall size and swelling went down. Her breast doctor did an ultrasound and said both breast were affected, but only the right breast was hurting.The rash was there but patient hoped it would go away.Patient took a picture on Sunday to show her doctor and at that point, where it was inflamed, was the actual redness of the rash. It was the bottom part that was inflamed and had a lump and redness. The redness could have been from the area that was like engorged. Patient enquired if this happened to anyone else. Patient took Claritin yesterday and the rash on her chest started to really go away. No further details provided for the Claritin. The rash did not go anywhere behind her. Patient saw her doctor for her annual gynecologist on Tuesday and told her to go see her breast doctor. Patient saw her breast doctor and her opinion was that it may have triggered glands that would make milk. Therapeutic measures were taken as a results of events right breast milk ducts inflamed, patient had rash on right breast ,patient reported that rash was going down chest, on both breast and front of neck. The Outcome of the reported events for the right breast milk ducts inflamed, rash on right breast and rash going down chest, on both breast and front of neck was recovering and unknown for all other events.  No follow-up attempts are possible; information about lot/batch number cannot be obtained.