Our patient cohort included seven men and six women aged 36–88 years. Three patients presented with abdominal distension and epigastric pain, and two with low-level fever. The other eight asymptomatic cases were detected during health checkups. In these eight cases, physical examinations revealed no signs of tenderness or rebound tenderness. Only one case had an increased white blood cell count before surgery. The white blood cell count and C-reactive protein levels were high at 19.5×109/L and 31.1 mg/L, respectively, whereas alpha-fetoprotein, carcinoembryonic antigen, carbohydrate antigen 125, and carbohydrate antigen 19-9 were within the normal range. Both hepatitis B virus surface antigen and antibody were negative. All tumors were resected without radiological recurrence during the follow-up periods of 10–24 months.
The clinical manifestations of IPT-like FDCS and comparison in liver and spleen are listed in Tables 2 and 3. No statistically significant differences were found for either sex, clinical manifestation, median age, or the number of nodules.
Multi-detector computed tomography findings
The imaging characteristics of IPT-like FDCS differed slightly between the liver and spleen (Table 4). Most unenhanced CTs showed a circular or quasi-round, slightly hypodense mass with a clear boundary. The tumor density was homogeneous in five cases. Obvious necrosis was found in three cases, and no calcification or bleeding was detected. The tumors in the liver were slightly enhanced in the arterial phase, decreased in the portal and delayed phases, and showed slightly lower densities than the liver parenchyma (Fig. 1). Splenic tumors showed mild continuous enhancement in five cases. Because the tumor enhancement was lower than that of the parenchyma, the lesions were always hypodense, and annular enhancement was seen in the delayed phase (Fig. 2 a-d). In the other two cases, the tumors in the spleen were significantly enhanced, and one of them showed honeycomb changes. The solid part showed heterogeneous enhancement after contrast administration sparing the central necrotic part (Fig. 3).
All liver tumors demonstrated slightly hypointense signals on T1-weighted imaging(Fig. 4a) and slightly hyperintense signals on T2-weighted imaging, with unclear edges and “halo sign” present in 2 of 3 cases (67%)(Fig. 4b). The diffusion-weighted imaging sequence showed slightly high or high signal intensities. (Fig. 4c) The liver lesions demonstrated substantial enhancements from the center to the periphery in the arterial phase(Fig. 4d). The enhancement amplitude of the lesions in the portal, venous, and delayed phases tended to be homogeneous and decreased in varying degrees, and annular enhancements could be seen (Fig. 4e,f). Seven of the nine cases with splenic lesions showed slight hyperintensities on T1-weighted imaging(Fig. 5a), slight hypointensities on T2-weighted imaging(Fig. 5b), slightly high or high signal intensities on diffusion-weighted imaging(Fig. 5c), and a hypointense ring on T2-weighted imaging could be seen at the lesion margin(Fig. 5b). There was mild-to-moderate heterogeneous enhancement; after enhancement, the amplitude was always lower than that of the normal spleen tissue, and annular enhancement could also be seen in the delayed phase (Fig. 5d-g). Significant differences between liver and spleen IPT-like FDCSs were found when comparing T1 and T2 signal intensities, enhancement patterns, and the presence of “halo signs” (Table 4).
Two-dimensional ultrasound demonstrated round-like lesions inside the spleen, with clear boundaries in two cases Fig. 2e), unclear boundaries in the other two cases, and homogeneous and heterogeneous hypoechogenicity in two cases each. Patchy, slightly hyperechoic, and small dark areas could be seen in one case, and a small dark area could be seen in another case. Strip or short-rod vascular signals could be seen in tumors with a pulse wave registered in the center and at the margins on color Doppler, and their velocity ranged from 90 to 140 cm/s. Only one case underwent contrast-enhanced ultrasound imaging and showed slight and rapid heterogeneous enhancement from the periphery to the center. Not only did the enhancement appear slightly earlier in the tumor than in the surrounding tissue, but it disappeared earlier as well. The number of cases examined by ultrasound was too low for statistical analyses.
The histology of the IPT-like FDCS in both liver and spleen is very similar to that of classical FDCS with a more prominent inflammatory component. Macroscopically, masses were round or nodular with diameters ranging from 3.5 to 12.0 cm (average 6.5 cm). Sections were solid and grayish-white with clear boundaries, and fibrous pseudocapsules with vitreous degeneration could be seen (Fig. 5i) pushing the surrounding tissue. Necrosis was detected in the center of the larger lesions in three cases. Histologically, the tumors were composed of fusiform or epithelioid cells, arranged in a whirlpool, diffuse sheet, or bundle shape, and fibrous pseudocapsule with vitreous degeneration was confirmed (Fig. 5h). The tumor cells showed a syncytial shape with an unclear boundary, and the rich cytoplasm was reddish. The tumors were mainly composed of an admixture of lymphocytes, plasma cells, and spindle cells. Nuclei were mild-to-moderate atypical, large, round or oval, vacuolar or finely granular, sometimes with pseudoinclusion bodies. Mitosis varied, and multinucleated giant cells were seen in some cases. IPT-like FDCS in the liver had a rich distribution of small blood vessels and capillary networks (Fig. 4g,h). The vascular distribution could also be seen in the fibrous capsule of some IPT-like FDCSs (Fig. 2f). Immunophenotypically, the tumor cells were strongly positive for CD21 and CD35 in 13 cases and for CD23 in three cases. Clusterin staining showed strong positive expression in the cytoplasm in three cases. Some tumor cells were positive for CD68, smooth muscle actin, vimentin, or epidermal growth factor receptor. The Ki-67 index was 5–30%. All cases were positive for the Epstein–Barr encoding region.
Treatment outcomes and follow-up
All 13 patients underwent surgical excision without adjuvant chemotherapy. The tumors were resected, and splenectomy and/or right or left hepatectomy and wedge resection of the liver were performed, accordingly. All cases were followed up postoperatively for periods ranging from 10 months to two years and did not exhibit local recurrence or distant metastasis.