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Rationale: Inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) of the liver is rare. It was previously believed that Epstein-Barr virus (EBV) positivity was a necessary criterion for pathological diagnosis. However, we found that there were also cases of EBV negativity. Therefore, clinicians and pathologists are reminded that EBV positivity is not a necessary condition for diagnosis., Patient Concerns: A 70-year-old female underwent computed tomography (CT) examination for upper abdominal discomfort, which revealed the presence of a liver tumor. Follow-up revealed that the tumor had progressively increased in size., Diagnosis: The final diagnosis was an IPT-like follicular cell sarcoma, based on CT, MRI, HE staining, and immunohistochemical staining., Interventions: The patient underwent a laparoscopic left hemihepatectomy., Outcomes: The patient has not undergone any special treatment, such as radiotherapy and chemotherapy, and has been followed up for over 3 years without experiencing any recurrence., Lessons: IPT-like FDCS is a rare tumor that lacks definitive criteria, and its diagnosis mainly relies on pathological findings. Previously, it was believed that being EBV-positive was an important condition for diagnosis. Primary IPT-like FDCS in the liver is even rarer, and the patient in this case tested negative for EBV. It may be necessary for pathologists to consider the role of EBV in the diagnosis of IPT-like FDCS., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Epstein-Barr virus-positive inflammatory follicular dendritic cell sarcoma (EBV+IFDCS) is a rare disease characterized by mild clinical symptoms and non-specific imaging findings. The diagnosis of the disease depends on pathological diagnosis. However, EBV+IFDCS has a very broad spectrum of histological morphology and immune phenotypes, and its histopathological features have not been fully described by pathologists., Case Presentation: A 59-year-old female, with no significant discomfort, was found to have a splenic mass during a routine physical examination. Microscopic examination at low magnification revealed numerous epithelioid granulomas, amidst which a substantial inflammatory response was observed. Interspersed among the dense inflammatory cells were spindle or oval-shaped cells, distributed sporadically with indistinct boundaries. Under high magnification, these spindle cells had subtle features: smooth and clear nuclear membranes, inconspicuous small nucleoli, and infrequent mitotic figures. Immunophenotypically, the spindle cells expressed CD21 and CD23, and Epstein-Barr encoding region (EBER) in situ hybridization yielded positive results. The inflammatory milieu predominantly consisted of T cells, with a minority of plasma cells expressing IgG4. The confluence of morphological and immunohistochemical findings led to the final pathological diagnosis of EBV+IFDCS in this case., Conclusions: The presentation of EBV+IFDCS with pronounced granulomatous changes is rare. This morphological variant poses a high risk of misdiagnosis, frequently leading to confusion with other granulomatous diseases. Accurate diagnosis necessitates a comprehensive analysis, integrating immunohistochemistry and in situ hybridization. The case presented here is instrumental in raising awareness and understanding of EBV+IFDCS, with the goal of reducing misdiagnoses and unrecognized cases., (© 2024. The Author(s).)

Background: Inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) is often associated with Epstein-Barr (EB) virus infection. The tumor is commonly found in the spleen and liver, and it has been reported in the literature that it can be associated with paraneoplastic pemphigus, myasthenia gravis, and other diseases. A case of IPT-like FDCS with clinical features of thrombocytopenia has not been reported., Patient Concerns: A 59-year-old male patient visited our hospital in September 2020 due to bleeding gums and epistaxis., Diagnosis: Splenic lymphoma with marked thrombocytopenia was initially diagnosed. The patient underwent pathological examination after splenectomy. Microscopic examination showed spindle-shaped or oval cells arranged in loose bundles, a large number of lymphocytes and plasma cells infiltrating the interstitium, and fibrin-like changes in the blood vessel wall. Immunohistochemical detection of tumor cells was positive for CD21, CD35, and Epstein-Barr virus in situ hybridization, and the patient was diagnosed with IPT-like FDCS., Interventions: The patient underwent a splenectomy. The patient received platelet-raising therapy postoperatively., Outcomes: No tumor recurrence or metastasis was found during the 17-month follow-up period, and the platelet count returned to normal., Conclusion: IPT-like FDCS is an uncommon tumor, and its first presentation with marked thrombocytopenia is even rarer. The tumor was clinically and radiographically nonspecific. Definitive diagnosis relies on histopathological and immunohistochemical staining. IPT-like FDCS is biologically indolent and has a favorable prognosis., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.)

Follicular dendritic cell sarcoma (FDCS) can be divided into the conventional type, and the inflammatory pseudotumor (IPT)-like variant type. Epstein-Barr virus (EBV) infection is considered to be closely associated with the pathogenesis of IPT-like variant of FDCS. Hepatic FDCS has an exceedingly low incidence of only 29 cases reported, with most of these tumors being classified as the IPT-like type. We report a case of an IPT-like variant of FDCS of the liver in a 61-year old man who presented with no marked symptoms. The patient underwent laparoscopic surgery for the mass and was well during a 13-month follow-up periods. The postoperative pathological examination found a proliferation of spindle cells and a diffuse infiltration of inflammatory cells within the tumor. Immunohistochemistry revealed that neoplastic cells were positive for CD23, clusterin, fascin, and PD-L1, and weakly positive for CD35, SMA, and D2-40. The infiltrating lymphocytes were strongly positive for PD1, and IgG4-positive plasma cells were less than 10 cells/high-power field. In situ hybridization for Epstein-Barr virus encoded RNA (EBER) was negative. To our knowledge, the present case is the second case of hepatic IPT-like variant of FDCS without EBV involvement, indicating that EBV infection is not an absolute prerequisite for a diagnosis of the IPT-like variant of FDCS., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Splenic inflammatory pseudotumor (IPT) is an uncommon lesion with an inflammatory morphologic aspect that often poses a diagnostic challenge. The etiology of IPT can be infectious, autoimmune, reactive, or neoplastic. Splenic Epstein-Barr virus (EBV)-associated IPTs form a subset of splenic IPTs in which there is a spindle cell component infected by EBV. The best characterized and most frequent subgroup of splenic EBV-associated IPT is IPT-like follicular dendritic cell tumor. This review also focusses on EBV-associated splenic IPTs without follicular dendritic cell marker expression. These lesions are less well characterized, making the differential diagnosis with other splenic lesions even more difficult. Recently, increased numbers of immunoglobulin G4-positive plasma cells and the presence of numerous granulomas have been reported in EBV-associated IPTs, and this can add to the difficulties in recognizing the neoplastic nature of these lesions. Herein, we also review the epidemiology, clinical features, histologic morphology, immunohistochemistry, electron microscopy, and pathogenesis of EBV-associated IPTs.

Various splenic inflammatory pseudotumours are reported to be infected with Epstein-Barr virus (EBV), which is thought to be associated with the pathogenesis of the lesion. The term "inflammatory pseudotumour (IPT)-like follicular dendritic cell tumour", all cases of which are also EBV positive, has recently been proposed. Here, we describe the imaging findings of these splenic tumours and present the cases of an IPT-like follicular dendritic cell tumour and two EBV-positive inflammatory pseudotumours in two female patients and one male patient. These splenic lesions were found incidentally on pre-operative or post-operative screening or at medical check-up. CT performed on all three patients revealed low-density solitary masses in the spleen. MRI was performed on one patient; the solitary mass demonstrated isointensity on T(1) weighted images and low intensity on T(2) weighted images relative to the surrounding splenic parenchyma. Dynamic MRI study revealed that the mass did not enhance on the early phase but enhanced to the same degree as the surrounding splenic parenchyma on the delayed phase. The imaging findings are almost identical to those found in conventional IPT because the morphology is similar in both cases; however, attention should be paid to this new entity in the diagnosis of splenic lesions because of its neoplastic nature. Longer follow-up is also necessary for these patients compared with those with conventional IPT.