Inflammatory Pseudotumor-like Follicular Dendritic Cell Tumor of the Spleen with Extensive Histiocytic Granulomas and Necrosis: A Case Report and Literature Review
A 76-year-old man underwent abdominal-pelvic computed tomography for follow-up of previous gastric cancer (disease-free state for five years after radical subtotal gastrectomy). A newly developed splenic mass had been increasing in size for the previous six months (1.9 to 3.4 cm) (). There was no evidence of local recurrence or metastasis, even on positron emission tomography-computed tomography. A splenectomy was performed. A well-defined gray-whitish firm nodule (3.2 cm in greatest dimension) was detected (). Microscopically, the well-defined lesion was composed of an admixture of inflammatory cells and spindle cells in a background of numerous histiocytic granulomas and central coagulative necrosis (). The oval to spindle cells had pale or eosinophilic cytoplasms with indistinct cell borders. The nuclei were enlarged and twisted or irregularly folded. Small but distinct, centrally located nucleoli were often evident (). Mitotic figures were not found. The infiltrating reactive inflammatory cells were predominantly composed of lymphocytes, plasma cells, and a small number of eosinophils. The immunohistochemical results are as follows: CD35+ (), CD21-, smooth muscle actin (SMA)-, and anaplastic lymphoma kinase- in oval to spindle cells, mixed imfiltration of CD3+ and CD20+ lymphocytes, and CD68+ in histiocytes (). The Ki-67 labeling index was about 30% in spindle cells. EBV in situ hybridization (EBV-ISH) revealed diffuse and strong positivity in oval to spindle cells (). Special stains for bacteria, acid-fast bacilli and fungi showed no organisms.