case_images: PMC10640977_01
case_images: (A) Hematoxylin & Eosin (H&E), 20X and (B) 40X showing scattered spindled tumour cells with round to oval nuclear membrane, slightly decondensed chromatin and with prominent nucleoli in the stroma with prominent mixed inflammatory cells of predominantly small lymphocytes. (C) H&E, 40X highlighting the large vessels with pink hyaline degeneration. (D) EBER-by in-situ hybridization, 40X, positive in tumour cells. (E, F) CD21, 40X, positive in occasional tumour cells. (G) CD3, 40X, positive in many small T lymphocytes. (H) CD20, 40X, positive in small B lymphocytes, tumour cells are negative.
case_images: fonc-13-1266897-g001.jpg
case_images: PMC10640977_01_fonc-13-1266897-g001.jpg
case_images: f1
case_images: The biopsy of the left upper quadrant mass, however, revealed an apparently unrelated neoplasm with a heterogeneous infiltrate consisting mostly of small to intermediate-sized lymphocytes, histiocytes, and rare plasma cells interspersed with scattered neoplastic large spindle to ovoid cells with prominent nucleoli which only comprised approximately 5% of the cellular constituents ( Figures 1A-C ). These large neoplastic cells exhibited focal positivity for CD21 ( Figures 1E, F ) and strong expression of Epstein-Barr virus-encoded small RNA (EBER) by in situ hybridization ( Figure 1D ). These cells did not show expression of other markers associated with follicular dendritic or fibroblastic cell differentiation (CD23, D2-40, SMA) or markers for lymphoid (CD1a, CD3 ( Figure 1G ), CD4, CD8, CD10, CD15, CD19, CD20 ( Figure 1H ), CD30, CD79a, CD138, BCL6, OC2, PD-1, MUM1, PAX5), myeloid (CD33, CD34, CD56), histiocytic, (CD68, CD163, ALK-1, S100), and epithelial cells (PAN-CK). Representative images of the lesion on CT at diagnosis and post-therapy are shown in  Supplementary Figure 1 .
case_images: The lollipop plot shows oncogenic mutations of the STAT gene by Zehir et al. in which they performed Targeted sequencing of 10,000 clinical cases using the MSK-IMPACT assay. This shows 10 mutational variants present within the SH2 domain. The coiled-coil domain is represented by STAT_alpha and the DNA binding domain is represented by STAT_bind. The image is taken from the OncoKB  database. The site of the STAT3 p.Glu618Arg missense mutation identified in this case is represented by an Asterick in the above image.
case_images: fonc-13-1266897-g002.jpg
case_images: PMC10640977_01_fonc-13-1266897-g002.jpg
case_images: f2
case_images: The timeline of clinical events is outlined in  Supplementary Figure 2 .