Inflammatory pseudotumor-like follicular dendritic cell sarcoma of the spleen: a report of six cases with increased IgG4-positive plasma cells

Epstein-Barr virus-positive inflammatory follicular dendritic cell sarcoma: A brief report of a rare neoplasm diagnosed with cytopathology on a splenic biopsy

Splenic biopsies for cytology remain challenging due to the inherent difficulty in obtaining adequate samples and the paucity of literature on rare entities arising in the spleen. Among these, are tumors arising from blood vessels, lymphomas and rarely, mesenchymal dendritic cell neoplasms. An important but rarely considered entity primarily arising in the spleen is Epstein-Barr virus-positive inflammatory follicular dendritic cell sarcoma (EBV+ IFDCS). EBV+ IFDCS is an indolent neoplasm with useful cytomorphologic and distinct biologic characteristics that can be evaluated on fine-needle aspiration (FNA) cytology and small biopsies. In this report, we present a challenging case with the final diagnosis facilitated by cytomorphology and diagnostic markers in an ambiguous initial presentation.

Clinicopathological and molecular genetic insights into EBV-positive inflammatory follicular dendritic cell sarcoma

Epstein-Barr virus (EBV)-positive inflammatory follicular dendritic cell (FDC) sarcoma (EBV + IFDCS) is a rare entity, and its histopathological characteristics have not been fully described. This study aimed to investigate the clinical characteristics, pathological features, and molecular genetic profiles of EBV + IFDCS to improve our understanding of these lesions. A total of 12 EBV + IFDCS specimens were obtained from patients in our pathology diagnostic center. The clinical data, morphology, immunohistochemistry, in situ hybridization, and high-throughput DNA-targeted sequencing data were collected, and follow-up data were analyzed. These data were compared with those of 6 patients with traditional FDCS. The patients with EBV + IFDCS ranged from 21 to 84 years old, with a mean age of 52.3 years and a male-to-female ratio of 1:5. At the last follow-up, all patients were alive, with 2 experiencing recurrence and metastasis. In these cases, four were classified as the classical subtype, four as the angiomatoid/sclerosing subtype, and four as the lymphoma-like subtype, with two cases also exhibiting epithelioid granulomas. All patients exhibited heterogeneous expression of follicular dendritic cell markers (CD21, CD23, CD35, and CXCL13) alongside the fibroblast marker SMA, with significantly higher expressions of IgG4, EBER, and SMA in EBV + IFDCS patients compared to FDCS patients (P < 0.05). Conversely, SSTR2, EGFR, and STAT3 expression were significantly lower in the EBV + IFDCS group (P < 0.05). The average value of EBER was significantly higher in the classical subtype group (P = 0.022). Among the four cases of EBV + IFDCS analyzed for molecular genetic features, one patient exhibited germline mutations in the CDKN1C, PDGFRA, MSH2, FANCG, MLH1, ALK, and RUNX1 genes; three exhibited simultaneous SNP variations in the MTHFR gene; and two exhibited simultaneous SNP variations in the NQO1 gene. We conducted KEGG pathway analysis on the mutant genes, revealing significant enrichment in the cAMP signaling pathway, which plays a crucial role in tumor development. Survival analysis demonstrated that the median PFS rates were not reached (NR) for EBV + IFDCS patients, compared to 5 months (HR = 7.76) for FDCS patients. The 3-year PFS rates were 66.67% and 16.67%, respectively. Compared with the FDCS group, EBV + IFDCS patients had a significantly longer median PFS time (p < 0.05). In conclusion, EBV + IFDCS represents a group of tumors with unique clinical, morphological, immunological, prognostic, and molecular cytogenetic characteristics.

A rare case of an EBV-positive inflammatory follicular dendritic cell tumor of the spleen

Epstein-Barr virus positive inflammatory pseudotumor follicular dendritic cell sarcoma (EBV+ FDCS) is a rare indolent neoplasm that presents primarily in the spleen and liver. We display a case of EBV+ FDCS in the spleen, its clinic-pathologic properties, and treatment. Our patient was evaluated following an incidental finding of a splenic mass on imaging after a traumatic injury. Computed tomography and magnetic resonance imaging both confirmed a well-circumscribed lesion in the spleen. Consequently, the patient underwent a robotic-assisted diagnostic splenectomy. Histologic examination revealed portions of spleen with partial effacement of tissue architecture by a well-circumscribed nonencapsulated mass displaying atypical, spindled cells-positive for EBER (CISH), EBV LMP1, smooth muscle actin, and clusterin-mixed inflammatory elements, and interspersed small lymphocytes.

Epstein-barr virus (EBV)-positive inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) presenting as thrombocytopenia: A case report and literature review

Background

Follicular dendritic cell sarcoma (FDCS) represents an exceedingly rare malignant neoplasm. Inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) is recognized as a variant manifestation of FDCS. The clinical incidence of this particular disease is remarkably low, resulting in the absence of established standardized clinical protocols for its management and treatment.

Methods

Presented here is a case of primary Epstein-Barr virus (EBV)-positive splenic IPT-like FDCS, noteworthy for manifesting thrombocytopenia as its initial symptom. Our study analyzed the clinicopathologic characteristics of this case and 29 previously reported cases identified in the literature. Also, we conducted a comprehensive review of pertinent literature.

Results

We administered splenectomy to this patient and verified the diagnosis of EBV-positive IPT-like FDCS through immunohistochemical examination. Postoperatively, the patient underwent a one-year follow-up period, demonstrating no signs of recurrence. Analyzing a total of 30 cases revealed that this disease is more prevalent in female patients (F:M = 1.14:1), with a median age of 62 years. Fifteen patients were asymptomatic, and nine patients presented with abdominal discomfort or pain. All patients underwent surgical treatment. Among the cases, histopathological and immunohistochemical information was unavailable for five; however, in the remaining 25 cases, histopathology revealed a distinct inflammatory cell infiltration and spindle tumor cells arranged in sheets or fascicles. These tumor cells had vesicular chromatin and distinct nucleoli and they expressed conventional FDC markers. In situ hybridization analysis of Epstein-Barr virus-encoded small RNA (EBER) showed that all 30 cases were EBV-positive. Follow-up information showed that no patients relapsed and one (3.8 %) patient died.

Conclusion

The clinical diagnosis of EBV-positive IPT-like FDCS poses considerable challenges, necessitating a conclusive diagnosis through pathological immunohistochemical examination. EBER in situ hybridization holds significance for the definitive diagnosis of the disease. We advocate for splenectomy as the treatment of choice for limited splenic IPT-like FDCS.

EBV-positive inflammatory follicular dendritic cell sarcoma of the colon with clonal immunoglobulin gene rearrangement: A case report and literature review

Introduction

Epstein-Barr virus-positive (EBV+) inflammatory follicular dendritic cell (FDC) sarcoma is a rare neoplasm characterized by spindle-shaped follicular dendritic cells, marked lymphoplasmacytic infiltration, and a consistent link to EBV. While it typically affects the liver and spleen, it is exceptionally rare in the digestive tract. We present a special case of EBV + inflammatory FDC sarcoma arising in the colon with clonal immunoglobulin (IG) gene rearrangement.

Case presentation

A 70-year-old man presented with a one-month history of abdominal distension. Colonoscopy revealed a pedunculated polyp in the ascending colon, which was subsequently removed via endoscopic polypectomy. Histological examination of the colonic polyp demonstrated a pronounced lymphoplasmacytic infiltrate with scattered EBV + neoplastic cells, as evidenced by EBV-encoded small RNA in situ hybridization (EBER ISH). The neoplastic cells were positive for FDC-specific markers, including CD21, CD35, and CD23. Additionally, the tumor exhibited clonal rearrangement of the immunoglobulin heavy chain (IGH) gene. The diagnosis was confirmed as EBV + inflammatory follicular dendritic cell sarcoma.

Conclusions

We described an exceptional case of EBV + inflammatory FDC sarcoma presenting as a colonic polyp, featuring a clonal IGH gene rearrangement not previously documented in this colonic tumor type. Heightened awareness of this rare neoplasm within the gastrointestinal tract is essential for both accurate diagnosis and effective patient management.

Clinicopathologic profile of intra-abdominal follicular dendritic cell sarcoma: A study of three cases with a literature review

Follicular dendritic cell sarcoma (FDCS) is a rare tumor, which mainly originates from follicular dendritic cells (FDCs) in the lymph nodes. Sometimes FDCS can arise from outside the lymph nodes. FDCS is an extremely rare malignant tumor in intraperitoneal or retroperitoneal tissue. We gathered the detailed clinical data of three patients diagnosed with FDCS in the abdomen. The clinical observations and histopathologic and immunohistochemical features of FDCS were analyzed. The patients included two men and one woman aged 55 ~ 61 years old. The mesentery of the small intestine and colon was involved in case 1, spleen in case 2, and retroperitoneal tissues in case 3. Two patients presented with abdominal masses, and one presented with no obvious symptoms. Histology showed ovoid to spindle neoplastic cells arranged in fascicles and storiforms with inflammatory infiltrate as well as whorled patterns in some areas. Immunohistochemical staining was positive for CD21, CD23, CD35, and SSTR2. FDCS exhibits no characteristic clinical manifestations. Morphologically, FDCS can have overlapping features with many other entities, leading to misdiagnosis. The use of histopathology supplemented with FDC markers, such as CD21, CD23, and CD35, is useful for diagnosis and differential diagnosis.

Laryngeal EBV-positive Inflammatory Follicular Dendritic cell/fibroblastic Reticular cell Tumour

Epstein-Barr virus-positive Inflammatory follicular dendritic cell/fibroblastic reticular cell tumour (EBV-IFDC/FRCT) is a rare neoplasm that occurs almost exclusively in the liver or spleen. Extra-hepatosplenic presentation is infrequent and exceptional cases have been described arising in the gastrointestinal tract or in the pharynx. However, EBV-IFDC/FRCT cases have not been previously reported in the larynx. This report describes a case of a 32-year-old woman who arrived to the emergency department due to progressive dyspnea with associated inspiratory stridor and non-productive cough. Direct laryngoscopy showed a nodular tumour arising on the left posterior subglottic mucosa obstructing 90% of the airway. A preoperative dual energy contrast enhanced computed tomography (CECT) was performed demonstrating a low attenuation lesion on virtual non-contrast (VNC) images and vivid iodine uptake on the iodine map. The tumour was excised and the histopathological analysis led to the diagnosis of an EBV-IFDC/FRCT. A fibre-optic laryngoscopy six months after the surgery did not show any abnormalities. Although the vast majority of EBV-IFDC/FRCT occur in the liver or spleen, some extra hepatosplenic tumours have been reported affecting the head and neck region. We describe here the first case arising in the larynx, as well as the usefulness of preoperative dual energy imaging techniques to assess these lesions, thus providing information that could have management implications.

Epstein-Barr Virus-Positive Inflammatory Follicular Dendritic Cell Sarcoma Presenting as a Colonic Polyp: Report of a Case with a Literature Review

Background: Follicular dendritic cell (FDC) sarcoma is an uncommon mesenchymal origin neoplasm derived from the abnormal proliferation and differentiation of FDCs. Epstein‒Barr virus-positive inflammatory follicular dendritic cell sarcoma (EBV+ iFDCS), which used to be known as the inflammatory pseudotumour (IPT)-like variant, occurs exclusively in the liver and spleen and has rarely been reported in the gastrointestinal tract. Case study: Here, we report a case of a 52-year-old woman with a special family history undergoing a routine physical examination. The colonoscope revealed an approximately 18 mm transverse colonic polyp, and the endoscopic polypectomy was performed. Microscopically, the excised polypoid mass was composed predominantly of inflammatory cells scattered with atypical ovoid to spindle tumor cells. Interestingly, there was a remarkable infiltration of IgG4+ cells. Immunohistochemistry showed that the tumor cells were positive for CD21, CD23 and CD35. EBV-encoded mRNA (EBER) in situ hybridization also gave positive signals. These histopathology features supported the diagnosis of EBV+ iFDCS. The patient was free of disease over 1-year follow-up. Conclusion: Identification of the potential pathogenesis sites of EBV+ iFDCS in extra-hepatosplenic regions is necessary for correct and timely diagnosis, and we consider it very meaningful to share our experience of diagnosing this tumor type. Furthermore, we summarize the clinicopathological features of EBV+ iFDCS presenting as a colon polyp after a thorough review of the literature.

Case report: Hepatic inflammatory pseudotumor-like follicular dendritic cell sarcoma: a rare case and review of the literature

Inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) is a rare subtype of follicular dendritic cell sarcoma (FDCS) that primarily occurs in the liver and spleen. The etiology of IPT-like FDCS is unknown, and it has nonspecific clinical manifestations, imaging performance and laboratory test results. Recently, a patient with IPT-like FDCS was admitted to our hospital because of abdominal distension and anemia. Over the past 3 years, the patient has been followed up after a liver mass was found in a physical examination. The lesion gradually enlarged and caused compression symptoms. In November 2022, a tumor with a diameter of approximately 20 cm was found in the right posterior lobe of the liver after abdominal enhanced Magnetic resonance imaging (MRI) in our hospital. Liver tumor biopsy before the operation revealed a large number of hyperplastic plasma cells and a small number of spindle cells, and the spindle cells were atypical. After a complete examination, the patient underwent liver resection. Pathology after surgery confirmed liver IPT-like FDCS.

Challenges in the Diagnosis of Epstein-Barr Virus-positive Inflammatory Follicular Dendritic Cell Sarcoma: Extremely Wide Morphologic Spectrum and Immunophenotype

Epstein-Barr virus (EBV)-positive inflammatory follicular dendritic cell (FDC) sarcoma (EBV + IFDCS) is a rare entity, and its histopathological characteristics have not been fully described. Here, we investigated the wide morphologic spectrum and immunophenotype of this tumor with the aim to help avoid misdiagnosis. Thirteen cases of EBV + IFDCS were retrospectively analyzed, combined with a review of 70 cases reported in the literature. The median age of patients was 49 (range, 29 to 67 y). Six patients were male and 7 were female. Most cases (92.3%, 12/13) occurred in the liver or spleen, and only 1 case affected an extra-hepatosplenic site (lung, 7.7%, 1/13). Tumors were assessed for a variety of histologic features and assigned to the following morphologic groups: classic type (53.8%, 7/13), lymphoma-like subtype (38.5%, 5/13), and hemangioma-like subtype (7.7%, 1/13). The classic type had distinct EBV-positive neoplastic cells with a fascicular or storiform growth pattern, variable lymphoplasmacytic infiltrates, and blood vessels. The lymphoma-like subtype had extremely prominent lymphoplasmacytic infiltrates (resembling marginal zone lymphoma with plasmacytoid differentiation) with singly dispersed distinct EBV-positive neoplastic cells, highlighted by in situ hybridization for EBV-encoded small RNA. The hemangioma-like subtype had extremely prominent blood vessels with hyaline and/or fibrinoid degeneration, singly dispersed distinct EBV-positive neoplastic cells, and limited lymphoplasmacytic infiltrates. Immunohistochemically, the neoplastic cells showed variable staining for FDC markers (CD21, CD35, CD23, and SSTR2) and the fibroblastic marker SMA, with the staining ranging from very focal to extensive. The number of EBV-positive neoplastic cells ranged from 80 to 400/HPF. All cases showed variable expression of PD-ligand 1 (PD-L1) (CPS: 5-90). IgG4-positive cells ranged from rare up to 100/HPF. Interestingly, 2 cases satisfied the criteria proposed in a previous study, mimicking IgG4-related disease. EBV + IFDCS is an entity with an extremely wide morphologic spectrum and immunophenotype. Awareness of the spectrum of morphologic presentations of this rare tumor, specifically the lymphoma-like subtype and hemangioma-like subtype, is important for accurate diagnosis.

Inflammatory pseudotumor-like follicular/fibroblastic dendritic cell sarcoma: focus on immunohistochemical profile and association with Epstein-Barr virus

Inflammatory pseudotumour-like follicular/fibroblastic dendritic cell sarcoma (IPT-like FDCS) is a rare EBV-associated variant of follicular dendritic cell sarcoma, usually arising in the liver or spleen and characterized by a favourable prognosis. The neoplastic cells show variable follicular dendritic cell or fibroblastic reticular cell differentiation and their immunoprofile is still poorly characterized. We describe a case of splenic IPT-like FDCS with unexpected CD31 expression and provide a concise review of English literature on the topic.

Surgical treatment of liver inflammatory pseudotumor-like follicular dendritic cell sarcoma: A case report

BACKGROUND

Inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) is rare with a low malignant potential. Hepatic IPT-like FDCS has similar clinical features to hepatocellular carcinoma (HCC), making it extremely difficult to distinguish between them in clinical practice. We describe the case of a young female patient diagnosed with HCC before surgery, which was pathologically diagnosed as IPT-like FDCS after the left half of the liver was resected. During 6 mo of follow-up, the patient recovered well with no signs of recurrence or metastasis.

CASE SUMMARY

A 23-year-old female patient with a 2-year history of hepatitis B presented to the Affiliated Hospital of Guizhou Medical University. She was asymptomatic at presentation, and the findings from routine laboratory examinations were normal except for slightly elevated alpha-fetoprotein levels. However, ultrasonography revealed a 3-cm diameter mass in the left hepatic lobe, and abdominal contrast-enhanced computed tomography revealed that the tumor had asymmetrical enhancement during the arterial phase, which declined during the portal venous phase, and had a pseudo-capsule appearance. Based on the findings from clinical assessments and imaging, the patient was diagnosed with HCC, for which she was hospitalized and had undergone laparoscopic left hepatectomy. However, the tumor specimens submitted for pathological analyses revealed IPT-like FDCS. After surgical removal of the tumor, the patient recovered. In addition, the patient continued to recover well during 6 mo of follow-up.

CONCLUSION

Hepatic IPT-like FDCS is difficult to distinguish from HCC. Hepatectomy may provide beneficial outcomes in non-metastatic hepatic IPT-like FDCS.

Case report: Hepatic inflammatory pseudotumor-like follicular dendritic cell sarcoma: A rare case and minireview of the literature

Inflammatory pseudotumor (IPT)-like follicular dendritic cell sarcoma (FDCS) is a rare neoplasm referred to as the FDCS variant. Here we report a 66-year-old female patient suffering from hepatic IPT-like FDCS and summarize IPT-like FDCS reported in the literature. The patient presented with obvious abdominal pain without significant laboratory abnormalities and subsequently underwent surgical resection of a hepatic lesion. Postoperative pathological results demonstrated a vascular tissue-rich neoplasm (7.0-cm maximum diameter). The tumor cells expressed CD21 and CD35, and in situ hybridization detected Epstein–Barr virus-encoded RNA (EBER). Metastasis or recurrence was not detected during the 7-year follow-up.

Inflammatory Myofibroblastic Tumour of the Sinonasal Tract with Orbital and Intracranial Extensions Simulating a Malignancy: A Case Report and Review of Literature

Inflammatory Myofibroblastic Tumour (IMT) is a rare pathology of unknown etiology. It is pathologically benign, but clinically locally invasive. We are herewith reporting a unique case of rapidly growing sinonasal IMT with orbital and intracranial extensions in a middle aged female patient masquerading as a malignancy. The lesion was excised endoscopically with margins and the patient is presently under close follow up. The report also reviews the common sites of involvement and management options available, based on a literature review.

Imaging and pathological comparison of inflammatory pseudotumor-like follicular dendritic cell sarcoma of the spleen: A case report and literature review

Background

Inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) is a rare subtype of follicular dendritic cell sarcoma (FDCS) that is mainly located in the liver and spleen (1). Splenic IPT-like FDCS is a rare low-grade malignancy with non-specific clinical manifestations and laboratory findings. Herein, we reported the pathological and imaging features of a case with splenic IPT-like FDCS.

Case presentation

A 57-year-old woman was found to have a mass in the spleen during a physical examination and was hospitalized for further treatment. Her laboratory results were within the normal range. Unenhanced and contrast-enhanced computed tomography scans of the whole abdomen showed a round mass in the spleen, with a diameter of about 5 cm. After further examination with enhanced MRI, a provisional diagnosis of splenic hemangioma or splenic hamartoma was made. The patient underwent splenectomy, and the pathological diagnosis was splenic IPT-like FDCS. No tumor recurrence or metastasis was found during the 1-year follow-up after the operation.

Conclusions

Herein, we reported a case of splenic IPT-like FDCS. Although the clinical examination and laboratory examination lack specificity, the imaging of this case showed that the lesion was a solid mass with progressive enhancement, and the central scar showed the characteristics of delayed enhancement, which facilitated the diagnosis.

Granulomatous splenic mass with necrosis revealing an EBV-positive inflammatory follicular dendritic cell sarcoma

Epstein-Barr virus-positive inflammatory follicular dendritic cell sarcoma is a variant of follicular dendritic cell neoplasm most often arising in the liver or spleen. Two histological patterns can be identified in this variant, namely a granulomatous and an eosinophil-rich one. We present the case of a 69-year-old woman with a splenic mass. After being removed, the mass was gray-whitish with an area of necrosis. Histology showed a diffuse distribution of epithelioid granulomas in a background of a dense lymphoplasmacytic infiltrate. Rare atypical cells EBV+ and CD21+ were present in the intergranulomatous areas. Differential diagnosis for the granulomatous type EBV+ inflammatory follicular dendritic cell sarcoma includes infection, sarcoidosis, inflammatory myofibroblastic tumor, T cell lymphoma and vasculitis. The origin of this neoplasm is the follicular dendritic cell, and, due to its similarities with a myofibroblast, differential diagnosis can be challenging. Immunohistochemistry for dendritic markers and in situ hybridization for EBER remain diagnostic keys.

Follicular dendritic cell sarcoma

Follicular dendritic cells (FDC) are mesenchymal-derived dendritic cells located in B-follicles where they play a pivotal role in triggering and maintaining B-cell adaptive immune response. In 1986 Dr. Juan Rosai first reported a series of neoplasms showing features of FDC and defined it as Follicular Dendritic Cell Tumor, subsequently renamed as "sarcoma" (FDCS). In its seminal and subsequent articles Rosai and colleagues highlighted the heterogeneous microscopic appearance of FDCS and its immunohistochemical and ultrastructural features.

FDCS mostly occurs in extranodal sites (79.4% of cases) and lymph nodes (15.1%); in about 7%-10% of cases it is associated with hyaline-vascular Castleman disease. Given its significant growth pattern and cytological variability, FDCS can be confused with various neoplasms and even inflammatory processes. The diagnosis requires the use of a broad spectrum of FDC markers (e.g. CD21, CD23, CD35, clusterin, CXCL13, podoplanin), particularly considering that tumor antigen-loss is frequent. The inflammatory-pseudotumor-like (IPT-like) variant of FDCS, in addition to its peculiar histopathological and clinical features, is characterized by positivity of tumor cells for Epstein-Barr virus, representing a diagnostic requisite.

No distinctive genetic and molecular anomalies have been identified in FDCS. It often carries an aberrant clonal karyotype and chromosomal structural alterations, frequently involving onco-suppressor genes. Direct or next generation sequencing showed alterations on genes belonging to the NF-κB regulatory pathway and cell-cycle regulators. In contrast to hematopoietic-derived histiocytic and dendritic cells tumors, FDCS typically lacks mutations in genes related to the MAPK pathway.

FDCS recurs locally in 28% and metastasizes in 27% of cases. Extent of the disease, surgical resectability and histopathological features are significantly associated with the outcome. IPT-like FDCS behaves as an indolent tumor, even if it often recurs locally over years.

Complete surgical excision is the gold standard of treatment. Data on targeted therapies (e.g.: tyrosine kinase inhibitors) or immune checkpoint inhibitors are very limited and responses are variable. A better understanding of the molecular drivers of this tumor may lead to potential new therapeutic strategies.

Inflammatory pseudotumor-like follicular dendritic cell tumor of the spleen: a case report and approach to differential diagnosis

We present a case of an inflammatory pseudotumor-like follicular dendritic cell tumor of the spleen. The patient is a 44-year-old woman, without significant underlying history, who presented with nonspecific abdominal pain for a few months. Both a contrast enhanced computed tomography and magnetic resonance imaging revealed a new 2.5 cm enhancing splenic lesion, which demonstrated hypermetabolic activity on subsequent positron emission tomography and computed tomography scan. Since the lesion was new compared to more remote imaging and hypermetabolic, a splenectomy was performed.  Pathology confirmed the diagnosis and demonstrated positivity for Epstein-Barr Virus .

Select Epstein-Barr Virus-Associated Digestive Tract Lesions for the Practicing Pathologist

CONTEXT.—

Epstein-Barr virus is a ubiquitous oncogenic virus. During the past 5 decades, the virus has been linked to several disease entities, both neoplastic and nonneoplastic. Several Epstein-Barr virus-associated conditions affect the digestive organs, ranging from mild transient inflammatory conditions to more debilitating and even fatal diseases.

OBJECTIVE.—

To discuss the clinicopathologic aspects of some newly or recently recognized Epstein-Barr virus-related conditions encountered in the digestive system and their therapeutic implications.

DATA SOURCES.—

Published peer-reviewed literature was reviewed.

CONCLUSIONS.—

This article highlights the importance of recognizing the discussed lesions because they influence the direct clinical management or serve as a potential predictive marker for therapy.

Inflammatory pseudotumor-like follicular dendritic cell sarcoma: Literature review of 67 cases

Inflammatory pseudotumor (IPT)-like follicular dendritic cell (FDC) sarcoma is rare. The 2017 World Health Organization classification of tumors of hematopoietic and lymphoid tissues noted that data on its clinical outcome are limited, but that the tumor appears to be indolent. The aim of this study was to summarize the clinical characteristics, treatment outcomes, and prognostic factors for IPT-like FDC sarcoma. A literature review was conducted on retrospective analyses of clinical data and prognostic information on IPT-like FDC sarcoma reported between 2001 and 2020. A total of 67 cases of IPT-like FDC sarcoma were retrieved from the literature, documenting that it occurs predominantly in middle-aged adults, with a marked female predilection. Six patients had a separate malignancy and five had an autoimmune disease. Typically involving the spleen and/or liver, it may also selectively involve the abdomen, gastrointes-tinal tract, pancreas, retroperitoneum, and mesentery. Necrosis, hemorrhage, noncaseating epithelioid granulomas, and fibrinoid deposits in blood vessel walls are often present. The neoplastic cells are predominantly positive for follicular dendritic cell markers such as cluster of differentiation 21 (CD21), CD23, CD35 and CNA.42 and are consistently Epstein-Barr virus (EBV)-positive. Mitoses were very rare in most cases. Most patients were treated by surgery alone. Disease status at the time of last follow-up was known for 57 patients with follow-up time ranging from 2 to 144 mo. Local and/or distant recurrence after initial treatment was seen in 15.8% of the patients. The 1- and 5-year progression-free survival for the entire group was 91.5% and 56.1%, respectively. Kaplan-Meier and multivariate analyses showed that age, sex, tumor size, and pathological features were not risk factors for disease progression. IPT-like FDC sarcoma appears to be mildly aggressive and requires annual surveillance. Surgery is the most effective treatment modality, and the role of adjuvant chemotherapy for postoperative management is unclear. EBV is likely to play an important role in the etiology of IPT-like FDC sarcoma.

Germinal Center Cells Turning to the Dark Side: Neoplasms of B Cells, Follicular Helper T Cells, and Follicular Dendritic Cells

Gaining knowledge of the neoplastic side of the three main cells—B cells, Follicular Helper T (Tfh) cells, and follicular dendritic cells (FDCs) —involved in the germinal center (GC) reaction can shed light toward further understanding the microuniverse that is the GC, opening the possibility of better treatments. This paper gives a review of the more complex underlying mechanisms involved in the malignant transformations that take place in the GC. Whilst our understanding of the biology of the GC-related B cell lymphomas has increased—this is not reviewed in detail here—the dark side involving neoplasms of Tfh cells and FDCs are poorly studied, in great part, due to their low incidence. The aggressive behavior of Tfh lymphomas and the metastatic potential of FDCs sarcomas make them clinically relevant, merit further attention and are the main focus of this review. Tfh cells and FDCs malignancies can often be misdiagnosed. The better understanding of these entities linked to their molecular and genetic characterization will lead to prediction of high-risk patients, better diagnosis, prognosis, and treatments based on molecular profiles.

A rare case of primary pulmonary inflammatory pseudotumor-like follicular dendritic cell sarcoma successfully treated by lobectomy

Primary pulmonary inflammatory pseudotumor-like follicular dendritic cell sarcoma (IPT-like FDCS) is extremely rare. Here, we report a case of a 64-year-old female with primary pulmonary IPT-like FDCS. The patient was found to have a solid nodule in the right lower lobe (RLL) of the lung incidentally without any symptoms or signs of discomfort. The chest computed tomography (CT) showed that there was an irregular nodule in the basal segment of the RLL, approximately 2.0 cm × 1.1 cm × 1.0 cm in size, of 15 HU in CT value. While the result of the fiberoptic bronchoscope-guided biopsy of the mass showed that there was inflammatory cell infiltration, no evidence of malignancy was found. After a thorough discussion of the multidisciplinary team, lobectomy of the RLL and systematic lymph node dissection were performed for the patient. Histologic analysis of the resected mass revealed infiltration of a large number of lymphocytes and plasma cells with the expression of CD21, CD23, CD35 were positive. In addition, the Epstein-Barr virus (EBV) probe in situ hybridization were positive. As a result, the diagnosis of EBV-positive IPT-like FDCS was strongly supported. No recurrence or any signs of metastasis were found during a 10-month follow-up time. As we have reported in this rare case, the diagnosis of primary pulmonary IPT-like FDCS should be considered even when there is only lymphoplasmacytic infiltration and no evidence of malignant tumor cells in the lung.

Epstein-Barr virus-negative inflammatory pseudotumor-like variant of follicular dendritic cell sarcoma of the liver: A case report and literature review

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.

Inflammatory pseudotumor-like follicular dendritic cell sarcoma: A brief report of two cases

BACKGROUND

Follicular dendritic cell (FDC) sarcoma/tumor is a rare malignant tumor of follicular dendritic cells, which is considered a low-grade sarcoma that can involve lymph nodes or extranodal sites. Conventional FDC sarcomas are negative for Epstein-Barr virus (EBV), whereas the inflammatory pseudotumor-like variant consistently shows EBV in the neoplastic cells.

CASE SUMMARY

We report two cases of inflammatory pseudotumor-like FDC sarcoma in the liver that received 3D laparoscopic right hepatectomy and open right hepatectomy separately.

CONCLUSION

EBV probe-based in situ hybridization and detection of immunohistochemical markers of FDC play an important role in the diagnosis and differential diagnosis of inflammatory pseudotumor-like FDC sarcoma. Complete surgical excision combined with regional lymphadenectomy may be effective in reducing the postoperative recurrence and metastasis and improving long-term survival rates.

Pancreatic Inflammatory Pseudotumor-Like Follicular Dendritic Cell Tumor

Follicular dendritic cell sarcoma (FDCS) is a rare and underdiagnosed malignant neoplasm which characteristically presents as a solitary, slow-growing mass with no discrete symptoms. Histologically, lymphocytes and spindle cells featuring large nucleoli in a whorled pattern are usually seen. FDCS is classically found in cervical and axillary lymph nodes, with occasional involvement of extranodal sites. Inflammatory pseudotumor-like follicular dendritic cell tumor (IPT-like FDCT) is an uncommon subcategory of this neoplasm, demonstratively linked to the Epstein-Barr virus (EBV). This neoplasm can present similarly to FDCS, but systemic symptoms may be seen. Although, often found in the spleen and occasionally the liver, IPT-like FDCT has not previously been described within the pancreas. Presented, is an IPT-like FDCT of the pancreas and spleen of a 70 years old woman. Histologic features include variably sized geographic suppurative granulomas with chronic inflammatory cells and an atypical spindle cell proliferation with prominent nucleoli. Positivity for CD45 and CD68 in the larger spindled cells points to an inflammatory pseudotumor subtype and co-expression of CD21, CD23, and CD35 were indicative of follicular dendritic differentiation. The pseudotumor additionally demonstrated EBV-encoded RNA (EBER) positivity typical of IPT-like FDCT. Differentiation between inflammatory pseudotumor (IPT) and inflammatory myofibroblastic tumor (IMT) is additionally discussed.

Histiocytic and Dendritic Cell Neoplasms

Histiocytic and dendritic cell neoplasms are very rare, belonging to a group that share morphologic, immunophenotypic, and ultrastructural characteristics of mature histiocytic/dendritic neoplasms. Histiocytic and dendritic cell neoplasms may arise de novo or in association with B-cell, T-cell, or myeloid neoplasms. Recent molecular findings, particularly the discoveries of the mutations in the RAS-RAF-MEK-ERK pathway, have greatly advanced the diagnosis and treatment options. Histiocytic and dendritic cell neoplasms may closely resemble each other, non-hematopoietic neoplasms, and even reactive processes. Therefore, it is essential to understand the clinicopathologic characteristics, differential diagnoses, and pitfalls of each entity.

Interdigitating dendritic cell sarcoma of the spleen with hepatic failure after chemotherapy: A case report

RATIONALE

Interdigitating dendritic cell sarcoma (IDCS) is an extremely rare disease originating from dendritic cells (DCs). There are few cases report interdigitating dendritic cell sarcoma of spleen along with their pathological characteristics and treatment.

PATIENT CONCERNS

Here we report a case of IDCS in 53-year-old female who presented spleen enlargement and thrombocytopenia.

DIAGNOSES

The patient underwent surgical resection of spleen, and the pathology confirmed IDCS.

INTERVENTIONS

She received surgical resection of spleen and one cycle of chemotherapy (ABVD with ifosfamide and oxaliplatin) after surgery.

OUTCOMES

She died of severe hepatic failure caused by chemotherapy.

DISCUSSION

IDCS is a rare disease with insufficient treatment guidelines. We adopted chemotherapy of ABVD with ifosfamide and oxaliplatin which showed no improvement but led to life-threatening liver damage.

Practical Applications in Immunohistochemistry: An Immunophenotypic Approach to the Spleen

CONTEXT.—

Even though immunohistochemistry is routinely used by pathologists, evaluation of immunohistochemistry in splenic lesions remains difficult for many. Classification of benign and splenic lesions often requires a combination of hematoxylin-eosin evaluation, immunophenotyping, and sometimes molecular testing. Immunohistochemical staining is essential in evaluating many splenic lesions, and requires an understanding of the normal compartments of the spleen.

OBJECTIVE.—

To address different immunohistochemical features used for identification and subclassification of different lesions of the spleen, as well as in the normal compartments of the spleen.

DATA SOURCES.—

The information outlined in this review article is based on our experiences with a variety of spleen cases, on the current World Health Organization classification of hematopoietic and lymphoid tumors, and on a review of English-language articles published during 2018.

CONCLUSIONS.—

Features for phenotyping normal spleen as well as a variety of splenic lesions, including littoral cell angioma and splenic marginal zone lymphoma, are discussed. Suggested immunopanels are provided to assist in the diagnosis of different lesions of the spleen.

Severe headache in a patient with meningioma showing extensive dural tail correlates with IgG4-positive plasma cells and eosinophils: A case report and review of literature

Background

Meningiomas originate from meningothelial cells of the arachnoid membrane. Few cases of meningioma with infiltration of inflammatory cells, such as lymphocytes and plasma cells, have been reported, and the mechanisms underlying meningioma-induced inflammatory reactions have not been fully elucidated.

Case Description

In this study, we report an extremely rare case of meningioma with infiltration of both IgG4-positive plasma cells and eosinophils showing extensive dural tail and reactive inflammation of the surrounding arachnoid tissue. The main clinical manifestation was a severe headache, which was improved by surgical excision of the tumor.

Conclusion

Only 8 cases of meningioma with IgG4-positive plasma cells have been reported, and only one case exhibited eosinophil infiltration. IgG4-related inflammatory response might mediate inflammation in surrounding tissue, resulting in thickening of the dura adjacent to a meningioma and severe headache. The mechanisms underlying inflammation by meningiomas require further investigation.

Interdigitating dendritic cell sarcoma located in the groin: a case report and literature review

Interdigitating dendritic cell sarcoma (IDCS) is an extremely rare subtype of dendritic cell neoplasms, and current knowledge on this tumor is limited. We herein report a case of an IDCS in a 64-year-old man who presented with a right inguinal mass combined with extensive retroperitoneal, pulmonary, hepatic, renal, and bone marrow infiltration. Because of the advanced stage of the disease, we performed five cycles of chemotherapy, including cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP); doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD); and ABVD combined with cisplatin, and one cycle of radiotherapy. The patient’s inguinal mass became smaller during the treatment, but there was no change in the extent of infiltration at the other sites. The patient died 8 months after the initial diagnosis. We also herein review the etiology, diagnosis, differential diagnosis, treatment, and prognosis of IDCS, and analyze the characteristics of IDCS in Chinese patients.

Inflammatory Pseudotumor-Like Follicular Dendritic Cell Sarcoma of the Spleen: Computed Tomography Imaging Characteristics in 5 Patients

OBJECTIVES

The purpose of this study was to retrospectively review the computed tomography (CT) and clinicopathological characteristics of inflammatory pseudotumor (IPT)-like follicular dendritic cell sarcoma (FDCS) of the spleen in 5 patients.

METHODS

Clinical, pathologic, and CT imaging findings of 5 patients with IPT-like FDCS of the spleen were reviewed and analyzed. Computed tomography imaging and pathologic features were compared.

RESULTS

Abdominal unenhanced CT revealed a well-defined hypodense mass in the spleen with complex internal architecture with focal necrosis and/or speckle-strip calcification. On postcontrast CT, slightly delayed enhancement was observed in 5 cases. Four patients had a normalized spleen. The fourth patient had lung metastasis. The fifth patient had 2 relatively small lesions as well as metastases to the spine.

CONCLUSIONS

Computed tomography imaging features of IPT-like FDCS of the spleen are distinctly different from other hypovascular splenic neoplasm; however, the definitive diagnosis requires further confirmation with needle biopsy or surgery. Inflammatory pseudotumor-like FDCS of the spleen should be suggested by using the CT imaging features of the splenic mass with evidence of metastatic disease.

Splenic Epstein-Barr Virus–Associated Inflammatory Pseudotumor

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.

Clinico-radiological and Pathological Characteristics of Inflammatory Myofibroblastic Tumors in Children: A Retrospective Study

Purpose

Inflammatory myofibroblastic tumors (IMTs) are rare, benign lesions most often seen in the lung of young adults but can occur in children, in various sites. They mimic, clinically and radiologically, malignant tumors - especially sarcomas and lymphomas. The aim was to review the clinical, radiological, and pathological data of children with a diagnosis of IMT referred to our department.

Materials and Methods

This retrospective study was conducted at the Department of Medical and Paediatric Oncology, Regional Cancer Centre, Sher-I-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India from January 2014 to December 2015.

Results

Among 288 pediatric tumors registered during the study, 5 (1.73%) had the diagnosis of IMTs. The main symptoms were abdominal distension and pain in 60% (three cases), breathlessness and cough in 20% (one case), and right axillary area swelling in 20% (one case). In three patients, complete surgical excision was done, whereas another patient with retroperitoneal mass had the residual disease and received chemotherapy followed by complete second surgery. In the case of mediastinal IMT, surgery was followed by local radiotherapy. At present, four patients are disease-free and one patient with mediastinal IMT has the residual progressive disease.

Conclusion

On presentation, IMT can constitute a formidable challenge, from diagnosis through to treatment.

Clinicopathological features of inflammatory pseudotumour-like follicular dendritic cell tumour of the abdomen

AIMS

Inflammatory pseudotumour-like follicular dendritic cell (FDC) tumour is an extremely rare neoplasm. Herein, we report 10 cases of inflammatory pseudotumour-like FDC tumours in the abdomen and analyse their clinicopathological features.

METHODS AND RESULTS

Seven patients were male, and three patients were female. The patients' age ranged from 28 years to 68 years (mean age, 52.9 years; median age, 51.5 years). Grossly, the tumour was usually solitary, well circumscribed, and solid, ranging from 23 mm to 233 mm in greatest diameter. Microscopically, the tumour was composed of variable amounts of spindle tumour cells with intense lymphoplasmacytic infiltrate. Unusual morphological findings, including eosinophils focally aggregated in one tumour admixed with multinucleated histiocytes in small clusters, fibrinoid deposits in the walls of ectatic blood vessel with occasional perivascular cuffs of lymphocytes, hyalinized fibrosis, and epithelioid granuloma, were identified. The tumour cells were immunoreactive for CD21, CD23, CD35, smooth muscle actin, and Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (7/10, 70%). EBV-encoded small RNA was positive in all cases by in situ hybridization. The recurrence rate was 10% with a median follow-up of 19 months.

CONCLUSIONS

Inflammatory pseudotumour-like FDC tumour should be differentiated from inflammatory myofibroblastic tumour, Hodgkin lymphoma, interdigitating dendritic cell sarcoma, and gastrointestinal stromal tumour.

Coexistence of gastrointestinal stromal tumor and inflammatory myofibroblastic tumor of the stomach presenting as a collision tumor: first case report and literature review

Collision tumors of the stomach are rare. We report on a case of a collision tumor consisting of a gastrointestinal stromal tumor (GIST) and an inflammatory myofibroblastic tumor (IMT) of the stomach in a 16-year-old female. A polypoid mass located in the distal body of the stomach was observed on abdominal computed tomography. Laparoscopic wedge resection of the stomach and 4d lymph node biopsy was performed. On gross examination, a protruding submucosal mass, measuring 4 × 3.5 × 2.5 cm in size, was detected. Histological examination showed two distinct GIST and IMT component presenting a collision tumor. The small nodular area, composed of CD117-positive spindle cells, was typical of GIST, and the adjacent larger area, composed of myofibroblastic spindle cells with prominent chronic inflammatory cells infiltrate, mainly lymphocytes and plasma cells, had a characteristic appearance of IMT. The 4d lymph node showed metastatic inflammatory myofibroblastic tumor. To the best of our knowledge, this is the first case of a collision tumor consisting of a GIST and an IMT arising in the stomach.

Epstein-Barr virus-associated inflammatory pseudotumor presenting as a colonic mass

Epstein-Barr virus (EBV)-positive inflammatory pseudotumor (IPT) commonly involves spleen and liver and has only rarely been reported in the gastrointestinal (GI) tract. The spindle cells may express myofibroblastic or follicular dendritic cell markers. We report a challenging case of EBV-positive IPT arising in the ascending colon. The lesion was composed of spindle cells positive for smooth muscle actin but negative for all follicular dendritic cell markers tested and was associated with an exuberant lymphoid proliferation containing reactive follicles, abundant plasma cells, and small lymphocytes. We further discuss pitfalls for possible misdiagnosis as ALK-positive inflammatory myofibroblastic tumor, IgG4-related disease, and peripheral T-cell lymphoma. Our case represents the first EBV-positive inflammatory pseudotumor of the GI tract in the Western literature. Awareness of this rare entity in GI tract is essential for correct diagnosis and appropriate patient management.

Inflammatory Pseudotumor of the Spleen

Isolated splenic inflammatory pseudotumors (IPT) are extremely rare, typically benign, inflammatory lesions with varied clinical presentations that pose a diagnostic challenge to clinicians due to their similarity in appearance to neoplasms. We present the case of a young woman diagnosed with a splenic IPT following investigation for persistent anemia, raised inflammatory markers, and polyclonal hypergammaglobulinemia, whose symptoms resolved completely following splenectomy. This case highlights the need to consider this diagnosis when evaluating patients with a splenic mass of unknown etiology.

Inflammatory pseudotumour-like follicular dendritic cell tumour of the spleen

We describe an unusual case of a 73-year-old woman presenting with a solitary splenic mass 8 cm in diameter and an elevation of serum soluble interleukin-2 receptor level. The preoperative diagnosis was primary malignant lymphoma of the spleen. Splenectomy was conducted. Histological analysis confirmed an inflammatory pseudotumour-like follicular dendritic cell tumour that showed different clinicopathological features from those of the classic follicular dendritic cell tumour. Only 33 cases of inflammatory pseudotumour-like follicular dendritic cell tumour have so far been reported. We discuss the incidence, presentation and management of this rare disease.

Inoperable inflammatory myofibroblastic tumour of the para-nasal sinuses and orbit with recurrence responding to methotrexate and prednisolone: a case report

BACKGROUND

Inflammatory myofibroblastic tumour is a rare neoplasm with a potential to behave in a malignant manner. It can occur anywhere in the body, however involvement of the head, especially the para-nasal sinuses is rare.

CASE PRESENTATION

A 33-year-old South Asian male presented with coryzal symptoms including a persistent cough with an asymmetrical swelling of the left side of the face. Imaging revealed a mass lesion involving the para-nasal sinuses eroding into the orbit. Histology and the clinical picture were compatible with inflammatory myofibroblastic tumour. As curative excision of the tumour was not feasible, medical management was offered. Despite early features of remission to glucocorticoids, tapering resulted in recurrence. Hence combination therapy with glucocorticoids and methotrexate was commenced with dramatic reduction of tumour burden and the patient has been in remission to date.

CONCLUSION

Inflammatory myofibroblastic tumour has the potential to behave in a malignant manner. Medical management with chemotherapy, glucocorticoids and non-steroidal anti-inflammatory drugs though effective, do not have a uniform response pattern. Surgically unresectable inflammatory myofibroblastic tumour above neck should be treated aggressively with combination regimens. Combination of prednisolone with methotrexate has been shown to have good outcome.

Extranodal follicular dendritic cell sarcoma: A clinicopathological report of four cases and a literature review

The aim of the present study was to characterize the clinicopathological features of follicular dendritic cell sarcoma (FDCS), and to report the experience of the Xin Hua Hospital Affiliated to Shanghai Jiaotong University School of Medicine (Shanghai, China) with this entity. The clinicopathological findings of four cases that had recently been encountered and 142 previously reported cases in the English literature were evaluated. The current tumors were found in two male and two female patients, aged 49–76 years old, who exhibited a mean tumor size of 8.7 cm. Three of the four cases were misdiagnosed during the initial diagnosis and one experienced intra-abdominal recurrence six months after the first diagnosis. Assessment of all 142 cases in the literature revealed a mild female predominance. The tumors exhibited a mean tumor size of ~7.0 cm. Histologically, the tumors were composed of plump spindle- or oval-shaped cells that exhibited eosinophilic cytoplasm and were arranged in sheets, storiform patterns or whorls. Immunohistochemically, the neoplastic cells expressed at least one of the FDC markers. Among the 130 cases with follow-up data, the overall recurrence, metastasis and mortality rates were 49.2% (64 cases), 21.5% (28 cases), and 13.8% (18 cases), respectively. FDCS can appear deceptively similar to other soft-tissue tumors, even poorly-differentiated carcinomas. A correct diagnosis requires a high degree of suspicion and immunohistochemical evaluation.

Splenic inflammatory pseudotumor-like follicular dendritic cell tumor

Inflammatory pseudotumor of the spleen with expression of follicular dendritic cell markers is an extremely rare lesion with only a few cases reported previously. The present study reports on an inflammatory pseudotumor of the spleen 10 × 8 × 7 cm in size that was incidentally found in a 61-year-old man and increased gradually in size during a period of 3 months. Abdominal ultrasonography revealed a well-circumscribed splenic mass, and abdominal computed tomography confirmed the presence of a well-circumscribed isodense lesion in the splenic hilum with inhomogenous enhancement in the early-phase images and no enhancement on delayed-phase contrast-enhanced images. Magnetic resonance imaging of the abdomen showed a well-defined isodense tumor on T1-weighted images with mildly increased signal intensity on T2-weighted images, and this is only the second study that provides MRI findings of this entity. The patient underwent an uncomplicated open splenectomy for definitive histologic diagnosis. Under microscopic examination, the lesion was an admixture of lymphocytes, plasma cells and spindle cells. In situ hybridization analysis for Epstein-Barr virus (EBV) revealed that most of the spindle cells were positive for EBV, and immunochemistry showed the expression of the follicular dendritic cell markers CD21, CD35 and CD23 within the tumor. The diagnosis of inflammatory pseudotumor-like follicular dendritic cell tumor was established.