Vaccination-associated reactive lymphadenopathy
D. Perform right axillary ultrasound now, with intent to biopsy enlarged lymph nodes
The keys to the correct diagnosis in this case were the recent receipt of COVID-19 vaccine 1 day prior to MRI, in conjunction with the lack of palpable axillary lymphadenopathy prior to vaccination. This presentation raised suspicion for vaccination-associated reactive lymphadenopathy; however, because of the patient’s recent diagnosis of ipsilateral breast cancer, a targeted axillary ultrasound with intent to biopsy enlarged lymph nodes (choice D) is the best answer. In the setting of newly diagnosed ipsilateral DCIS, the asymmetrically enlarged right axillary lymph nodes identified on MRI could represent an invasive tumor in addition to DCIS with potential axillary lymph node metastasis. Therefore, waiting 4 to 6 weeks (choices A and B) is not recommended. In the setting of DCIS, where less than 25% of patients are found to have invasive carcinoma on final pathology after surgical excision, sentinel lymph node biopsy is performed only in patients for whom the procedure cannot be technically performed as a second operation (eg, mastectomy or those in whom the DCIS excision is in an anatomical location that would compromise the breast lymphatics). For this patient, without a diagnosis of invasive carcinoma and in the setting of a planned medial breast lumpectomy that would not alter the lymphatic pathway to the axilla, sentinel lymph node biopsy (choice C) would not be recommended.