Purpose: Unilateral axillary lymphadenopathy (UAL) has been widely reported in association with messenger RNA (mRNA) COVID-19 vaccines. We aimed to assess outcomes of axillary lymph node biopsies before and after the widespread administration of mRNA-based COVID-19 vaccines. Understanding the rates of malignancy in UAL is important to guide patient management.
Materials and Methods: Imaging reports were queried for patients who underwent lymph node biopsies in the breast imaging department of two university affiliated breast centers between January 1, 2017, through December 31, 2022. The laterality of each biopsy, presence of a concomitant suspicious breast finding, personal history of intact or remote breast cancer, and personal history of other malignancies was recorded. Malignant biopsies were classified as either metastasis of breast cancer or other cancer metastasis. The number of lymph node biopsies performed in each quarter for the past five years due to isolated UAL and UAL with the presence of an ipsilateral breast finding, which served as a control, was calculated.
Results: 1,920 axillary lymph node biopsies were analyzed. Out of 165 axillary lymph node biopsies performed due to isolated UAL, 11 (6.7%) were malignant, of which 5 were primary breast cancer. In contrast, among 134 UAL biopsies in patients with a breast cancer history, 42 (31.3%) were metastatic breast cancer. For patients with isolated UAL, we noted a 136% increase in quarterly biopsy rates before vs. after January 2021 [mean 4.2 (Std 2.4) vs. 9.9 (Std 4.9), P=0.01]. In contrast, in patients with an ipsilateral breast abnormality, the UAL biopsy rate increased by 25% in the same period [mean 39.2 (Std 7.0) vs. 49.1 (Std 8.0), P=0.01]. From 2017-2020, the malignancy rate for biopsies due to isolated UAL was 10.1%, which decreased to 3.4% from 2021-2022. Conversely, biopsies resulting from an ipsilateral breast finding had a malignancy rate of 54.7% from 2017-2020, which increased to 56.7% from 2021-2022.
Conclusion: Since the introduction of mRNA vaccines for COVID-19, there has been an increase in the number of biopsies due to UAL and a decrease in the rate of malignancy at pathology. From 2017-2022, in patients without a suspicious breast finding or a history of breast cancer, the rate of malignancy for UAL was 6.7%.
Clinical Relevance Statement: This study illuminates the need to refine protocols for UAL, especially in the era of the mRNA COVID-19 vaccine, to maximize the diagnosis of cancer and minimize the number of biopsies performed.
