case_images: PMC8116528_01
case_images: Dorsal plane whole-body CT, fused PET/CT, gray-scale PET, and axial plane fused PET/CT at the level of the kidneys (left to right). Showing increased 18F-FDG uptake in the region of the left medial retropharyngeal lymph node mass, as well as the nasal tissues, nasopharynx, right lung, mediastinum, liver, and both kidneys. Histopathology post-mortem confirmed large-cell high-grade lymphoma causing increased uptake in the kidneys. The increased 18F-FDG uptake in the urinary bladder is a normal finding. The increased 18F-FDG uptake in the small intestine is likely due to normal digestion.
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case_images: PMC8116528_01_fvets-08-619264-g0001.jpg
case_images: F1
case_images: PET/CT (Figure 1) showed multiple enlarged 18F-FDG-avid lymph nodes (SUVmax left medial retropharyngeal 31.0; right medial retropharyngeal 4.5; left caudal cervical 19.5) and nodal masses in the neck, in addition to multiple 18F-FDG-avid regions in both lungs (SUVmax 4.4 and 6.8) and the mediastinal lymph nodes (SUVmax 10.6 and 17.6).
case_images: Evaluation of left retropharyngeal lymph node biopsy via H&E staining and immunohistochemistry (bar = 20 muM). (A) The neoplasm was composed of round neoplastic cells with little cytoplasm and nuclear pleomorphism. There are scattered neutrophils, macrophages, and nuclear debris (60x, H&E). The inset shows the entire biopsy specimen that was received (2x, H&E). (B) Rarely throughout the neoplasm, there were cells that appeared to have bilobed or binucleated nuclei with prominent eosinophilic nucleoli (within dotted line). These were suspect Reed-Sternberg cells and were not a prominent feature of the neoplasm (60x, H&E). (C) Neoplastic cells had strong membranous labeling with CD20, consistent with a B-cell neoplasm (60x, CD20 immunohistochemistry). The inset highlights the nodularity of the neoplasm with CD20+ cells surrounding foci of non-CD20, non-neoplastic cells (2x, CD20 immunohistochemistry). (D) There were scattered non-neoplastic lymphocytes that had strong membranous to cytoplasmic labeling for CD3 within the neoplastic population and within the non-neoplastic regions (60x, CD3 immunohistochemistry).
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case_images: PMC8116528_01_fvets-08-619264-g0002.jpg
case_images: F2
case_images: On low power, the neoplasm had vague and indistinct outlines of nodules composed of fibrous connective tissue (Figure 2A, inset). Neoplastic cells were round, had distinct cell borders, had variable amounts of eosinophilic to basophilic cytoplasm, and had large, round to irregular nuclei with vesicular to finely stippled chromatin and one large, eosinophilic, distinct nucleoli (Figure 2A). Rare (less than five) cells had nuclei that appear to be bilobed or binucleated with prominent eosinophilic nucleoli (suspect Reed-Sternberg cells) (Figure 2B). The neoplastic cells had strongly membranous labeling for CD20 (Figure 2C), and there was a distinct nodularity appreciated to the neoplasm (Figure 2C, inset). The neoplastic cells also had variably positive nuclear labeling for Pax5 (not pictured), but they were negative for CD3 (Figure 2D), supporting a diagnosis of large B-cell lymphoma. The described nodularity seen on H&E (Figure 2A, inset) and the CD20 stain (Figure 2C, inset) was further characterized with IHC with a histiocyte marker, Iba-1.
case_images: Evidence of multicentric disease confirmed at autopsy (bar = 20 muM). (A) Mandibular lymph node effaced with widespread neoplastic lymphocytes. Similar to the previous biopsy, there was an additional inflammatory infiltrate consistent with neutrophils, macrophages, and non-neoplastic lymphocytes (40x, H&E). (B) There were multifocal regions of neoplastic cells effacing parts of the renal cortical interstitium with loss of tubules. Many of the glomeruli (*) were left intact and surrounded by sheets of neoplastic cells (40x, H&E). (C) Neoplastic lymphocytes were clustered throughout the sections of liver corresponding to the tan to red masses seen grossly at autopsy. Additional microscopic foci of neoplastic cells extended into the sinusoids (40x, H&E).
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case_images: PMC8116528_01_fvets-08-619264-g0003.jpg
case_images: F3
case_images: Histopathology confirmed large-cell high-grade lymphoma within both retropharyngeal and mandibular lymph nodes (Figure 3A), kidneys (Figure 3B), and liver (Figure 3C).