PMC9845691_01
Brain MRI scans obtained from the patient and timeline of his clinical course. Despite there being no specific findings upon an initial T2-weighted MRI (A), mild cerebellar atrophy was observed in the subsequent axial T2-weighted MRI performed seven months later (B, yellow arrow). Timeline of the patient's clinical course highlighting the manifestation, auxiliary examination, treatment and diagnosis time (C). EEG, electroencephalograph; LE, limbic encephalitis; MMF, mycophenolate mofetil; MRI, magnetic resonance imaging; IVMP, intravenous methylprednisolone; PET/CT, positron emission tomography with computed tomography.
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Brain MRI showed mild cerebellar atrophy ( Figure 1B ). The evaluation of PNSs process is summarized in  Figure 1C .
Histopathology of appendiceal goblet cell carcinoma of the patient. Tumor cells exhibit a goblet cell morphology and characteristically form small tight clusters (A). The immunohistochemical staining shows moderate positivity for CK20 (B), CDX-2 (C), and strong positivity for carcinoembryonic antigen (CEA, D). Staining for synaptophysin (Syn, E), and chromogranin (F) is mild. Varying degrees of positivity are also shown in lymphocytes such as CD3+ T cells (G), CD8+ T cells (H) and CD20+ B cells (I). Immunohistochemistry shows positive staining for amphiphysin-IgG (J). Tissue-based indirect immunofluorescence assay (TBA) of the patient's serum detected fluorescence responses, with specific fluorescence responses in Purkinje cells (red arrows) from the monkey cerebellum brain section (K) as well as dentate gyrus glial cells (white arrows) from the monkey hippocampal tissue. (A,-C, G, J) bar = 50 microm; D, H bar = 250 microm; (E, F, O) bar = 100 microm, (K, L) bar = 20 microm).
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Immunohistochemical staining for CK20, CDX-2, carcinoembryonic antigen (CEA) and neuroendocrine markers (synaptophysin and chromogranin) were positive ( Figures 2A-F ), which meets the diagnostic pathological diagnostic criteria of Agcc according to the 2019 WHO.2 The expression of Ki67 protein was about 10%. Immunohistochemistry revealed positive CD3+ T cells, CD8+ T cells and CD20+ B cells in the tumor tissue ( Figures 2G-I ). Tumor cells showed reactivity with amphiphysin-Abs ( Figure 2H ), which indicates that the aGCC might play a role in triggering amphiphysin-IgG autoimmunity. Tissue-based indirect immunofluorescence assay (TBA) of the patient's serum revealed IgG antibody to Purkinje cells of the monkey cerebellum and dentate gyrus glia cells of the monkey hippocampus ( Figures 2K, L ).