Inflammatory Pseudotumor-Like Follicular Dendritic Cell Tumor

Abstract

Follicular dendritic cell (FDC) tumors are uncommon neoplasms that can involve lymph nodes or extranodal sites. They can exhibit a broad spectrum of histologic appearances and behavior, but the intra-abdominal ones usually pursue an aggressive course. The purpose of this study was to characterize a distinctive variant of FDC tumor morphologically mimicking inflammatory pseudotumor through analysis of the clinicopathologic features of 11 cases. The patients included 10 women and one man (age range, 19-61 years; median age, 40 years) who presented with abdominal discomfort or pain. Six patients had systemic symptoms such as marked weight loss, fever, or malaise. All tumors occurred in intra-abdominal sites: liver (n = 7), spleen (n = 3), and peripancreatic region (n = 1). Of the nine patients with follow-up data, six were alive and well, one developed recurrence at 9 years, and two had repeated recurrences over many years. Grossly, the tumors were usually solitary and fleshy, punctuated by areas of hemorrhage and necrosis. Histologically, in a background of abundant lymphocytes and plasma cells were dispersed spindle or ovoid cells with vesicular nuclei and distinct nucleoli. The degree of nuclear atypia was variable, and some nuclei could be grotesque or resemble Reed-Sternberg cells. Focally, spindle cell fascicles could be formed. The atypical cells were immunoreactive for FDC markers such as CD21/CD35, CD23, and CNA.42. In situ hybridization for Epstein-Barr virus (EBV)-encoded RNA was positive in all cases, remarkably highlighting the spindle cells and their atypia. EBV-latent membrane protein-1 was expressed commonly, albeit often focally and weakly. Therefore, inflammatory pseudotumor-like FDC tumor represents a distinctive variant of FDC tumor that differs from conventional FDC tumor in the following aspects: marked female predominance; selective localization in intra-abdominal sites, especially the liver and spleen; frequent presence of systemic symptoms; indolent behavior despite an intra-abdominal location; dispersed distribution of tumor cells and prominent lymphoplasmacytic infiltration; and consistent association with EBV.

Inflammatory Pseudotumor-like Follicular Dendritic Cell Tumor of the Spleen: Case Report and Review of the Literature

“…8 Most FDCTs arising at the liver or spleen are categorized as IPT-like FDCTs, and this type is rare at other sites. 4 IPT-like FDCTs arising at the liver or spleen are associated with EBV infection, whereas conventional FDC tumors show EBV association in only one of 25 cases (4%). [3][4][5] Thus, the identification of EBV infection is important in the diagnosis of IPT-like FDCTs by immunostaining for EBV-LMP, which is a protein product of EBV with transforming function, or by the detection of the EBER gene by in situ hybridization.…”

“…Histologically, FDCTs are characterized by the syncytial growth of spindle or ovoid cells, which are immunoreactive for such various FDC markers as CD21 and CD35. 4 A storiform or whorled growth pattern is frequently encountered. FDCTs are categorized into 2 types-conventional FDCTs composed of the storiform, fascicular, and diffuse growth of tumor cells with a sprinkling of lymphocytes and IPT-like FDCTs composed of dispersed tumor cells with intense lymphocytes and plasma cells.…”

“…FDCTs are categorized into 2 types-conventional FDCTs composed of the storiform, fascicular, and diffuse growth of tumor cells with a sprinkling of lymphocytes and IPT-like FDCTs composed of dispersed tumor cells with intense lymphocytes and plasma cells. 4 EBV-positive IPT is sometimes used instead of IPT-like FDCT to refer to this entity, but EBV-positive IPT and IPT-like FDCT may be considered the same disease entity, although more discussion is required. 8 Most FDCTs arising at the liver or spleen are categorized as IPT-like FDCTs, and this type is rare at other sites.…”

“…2 Splenic FDCTs are generally associated with Epstein-Barr virus (EBV) infection and are referred to as inflammatory pseudotumor (IPT)-like FDCTs because they resemble IPTs histologically. [3][4][5] Several reports provide imaging findings of splenic FDCTs on computed tomography (CT) and/or magnetic resonance (MR) imaging 6 -12 and describe the lesions as well circumscribed with delayed enhancement. 7,10 These imaging features resemble those of other splenic tumors, such as metastatic tumors, lymphomas, and IPTs, so preoperative diagnosis of FDCTs is difficult.…”

“…8 One pathological feature of FDCTs is the presence of a fibrous capsule between the tumor and the surrounding parenchyma. 4,6 To the best of our knowledge, the presence of capsular formation has rarely been referenced in the differential diagnoses of splenic tumors. The radiological detection of this capsule might be helpful to differentiate splenic IPT-like FDCTs from other splenic tumors.…”