Inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) is often associated with Epsrein-Barr (EB) virus infection. A male patient visited our hospital in September 2020 due to bleeding gums and epistaxis. The initial diagnosis was splenic lymphoma with marked thrombocytopenia. The patient was sent for pathological examination after splenectomy. Microscopic examination showed spindle-shaped or oval cells arranged in loose bundles, a large number of lymphocytes and plasma cells infiltrated in the interstitium, and fibrin-like changes in the blood vessel wall. Immunohistochemical detection of tumor cells was positive for CD21, CD35 and EBER, and we diagnosed IPT-like FDCS. The patient received platelet-raising therapy after operation. No tumor recurrence or metastasis was found during the 17-month follow-up, and the platelets returned to normal.IPT-like FDCS is an uncommon tumor, and the first presentation with marked thrombocytopenia is even rarer. The tumor was clinically and radiographically nonspecific. Its definitive diagnosis needs to rely on histopathological and immunohistochemical staining. IPT-like FDCS is biologically indolent and has a good prognosis.

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.