Kikuchi-Fujimoto-like lymphadenopathy following COVID-19 vaccine: diagnosis and management

Abstract

A woman in her mid 40s presented for breast imaging after 1 week of painful and enlarged right axillary lymphadenopathy. She denied history of fever, weight loss, night sweats fatigue, cat scratch or other trauma. She received the second dose of Pfizer COVID-19 vaccine 3 months previously on the contralateral arm. A mammogram demonstrated a single, asymmetric, large and dense right axillary lymph node. Ultrasound confirmed a 2.5 cm lymph node with cortical thickening of 0.6 cm. Ultrasound-guided core biopsy showed necrotising lymphadenitis with associated aggregates of histiocytes and plasmacytoid dendritic cells. Potential causes of necrotising adenitis including Bartonella, tuberculosis, Epstein-Barr Virus, herpes simplex virus, systemic lupus erythematosus and lymphoma were excluded. In the absence of any identifiable infectious or autoimmune causes, and given the temporal relatedness with vaccine administration, it was determined that the Kikuchi-Fujimoto-like necrotising lymphadenitis was likely secondary to the COVID-19 vaccine. To date, there has been no casual association made between the COVID-19 vaccine and KFD necrotising lymphadenitis.

Keywords: Immunological products and vaccines; Radiology.

Figure 1

Cropped right mediolateral oblique synthetic two-dimensional view showing an enlarged, dense right axillary mass with irregular margins (arrow) corresponding to the palpable abnormality as denoted by a triangular marker.

Figure 2

Right axillary ultrasound showed an enlarged axillary lymph node with a 0.6 cm hypoechoic cortex with mild hilar displacement (arrow) corresponding to the palpable and mammographic mass.

Figure 3

Ultrasound-guided core biopsy (arrow) with a 14-gauge needle and automated gun.

Figure 4

Histopathological features of lymph node biopsy. Core needle biopsies of lymph node showed multifocal necrotising lymphadenopathy characterised by foci of necrosis surrounded by reactive appearing small lymphoid cells, histiocytes and plasma cells. The interface of the viable reactive lymphoid cells (left of arrow) and the necrotic foci (right of arrow) is shown (A, H&E stain, ×40 magnification). Foci of necrosis showed apoptotic cellular debris and haemorrhage (B, H&E stain, ×40 magnification). The lymphoid cells at the interface and surrounding foci of necrosis are small and mature without overt cytological atypia (C, arrow; H&E stain, ×40 magnification). Immunohistochemistry testing confirmed the presence of small B cells expressing CD20 and small T cells expressing CD3, the former present in perinecrotic foci in the latter also present within necrotic foci. CD68 highlights reactive histiocytes present within necrotic foci (CD20, CD3 and CD68 immunohistochemistry stained slides, ×20 magnification). Not shown are negative for organisms stains including GMS fungal stain, acid–fast bacillus stain, Warthin-Starry silver stain, cytomegalovirus and herpes simplex virus immunohistochemistry stains.