Breast cancer; Developed knots under her armpit and under her breast; Developed knots under her armpit and under her breast; feel sensations in her breast; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP).  A 59 year-old female patient received bnt162b2 (BNT162B2), administered in arm, administration date 2021 (Batch/Lot number: unknown) at the age of 59 years as dose 1, single for covid-19 immunisation. Relevant medical history included: "Anxiety" (ongoing), notes: The caller stated that her sister had anxiety after she found out that she had cancer. The caller doesn't know when she was diagnosed. It was probably when the doctor told her she had cancer and the biopsies came back positive. It was a couple weeks ago. Family history included: "breast cancer metastasis to the bone and to the brain" (unspecified if ongoing), notes: mother at age 42 that had breast cancer metastasis to the bone and to the brain., . There were no concomitant medications. The following information was reported: BREAST CANCER (medically significant) with onset 2021, outcome "not recovered", described as "Breast cancer"; BREAST MASS (non-serious), LYMPHADENOPATHY (non-serious) all with onset 2021, outcome "not recovered" and all described as "Developed knots under her armpit and under her breast"; BREAST DISCOMFORT (non-serious) with onset 2021, outcome "not recovered", described as "feel sensations in her breast". The events "breast cancer", "developed knots under her armpit and under her breast", "developed knots under her armpit and under her breast" and "feel sensations in her breast" were evaluated at the physician office visit. The patient underwent the following laboratory tests and procedures: biopsy: (2021) positive, notes: 3 biopsies; magnetic resonance imaging: (Dec2021) unknown results; mammogram: (2021) positive. Therapeutic measures were taken as a result of breast cancer, breast mass, lymphadenopathy, breast discomfort.  Clinical course: Breast cancer was aggressive. Investigations:The mammogram and biopsy was done in the last 4 weeks and they were positive. The doctor called the patient to see the oncologist last Friday. The oncologist said to see the surgeon and the patient saw the surgeon the same day.The patient went back for an MRI this past Monday and then she went and saw the surgeon again. The surgeon said that they need to put a port in and she gets it Thursday and then she will start chemo #at a hospital area with the cancer institute. The caller stated that her sister has to have a bilateral mastectomy later. The caller's sister developed knots up under her armpit and in her breast. She has been diagnosed with breast cancer. She had a 3D mammogram and had 3 biopsies. She's undergoing chemo for 4 months. With the injection that she got, she immediately began to feel sensations in her breast, so she went for a mammogram. The doctor got biopsies and she's getting a port Thursday to begin chemo for 4 months.  Family Medical History Relevant to AE(s): The caller stated that they had a mother at age 42 that had breast cancer metastasis to the bone and to the brain. She died of a cerebral hemorrhage at age 47 in 1982. The caller stated that her mother didn't get any kind of vaccines. There was no such thing as COVID back then. Adverse Event: Developed knots under her armpit and under her breast Time of Onset: (24-hour clock): The caller stated that the time her sister got the injection and the time her sister developed the knots wasn't very long. Maybe two months, maybe less, she is not sure.  The lot number for bnt162b2 was not provided and will be requested during follow up.