Inflammatory Pseudotumor-like Follicular Dendritic Cell Tumor



Inflammatory Pseudotumor-like Follicular Dendritic Cell Tumor


Roberto N. Miranda, MD





Key Facts


Terminology



  • Inflammatory pseudotumor-like follicular dendritic cell tumor (IPT-FDCT)


  • Considered variant of follicular dendritic cell sarcoma


  • Classification is controversial


Clinical Issues



  • Marked female predominance


  • Good prognosis; no deaths attributable to IPT-FDCT of spleen


  • IPT-FDCT affecting liver can be recurrent and metastatic in rare cases


Microscopic Pathology



  • Well-demarcated single mass with occasional incomplete fibrous capsule


  • Loosely aggregated or dispersed oval or spindle cells admixed with abundant inflammatory cells


Ancillary Tests



  • Usual reactivity with follicular dendritic cell markers


  • Epstein-Barr virus encoded RNA (EBER)(+) in spindle cells in 40% of cases


  • Cases that are EBV(+) show that viral genome is monoclonal


Top Differential Diagnoses



  • Splenic inflammatory pseudotumor


  • Follicular dendritic cell sarcoma


  • Inflammatory myofibroblastic tumor


  • Sclerosing angiomatoid nodular transformation of red pulp







Inflammatory pseudotumor-like follicular dendritic cell tumor displays cellular image and sclerotic image areas. (Courtesy M. Vasef, MD.)






Inflammatory pseudotumor-like follicular dendritic cell tumor shows extensive necrosis image, which is a feature that may mislead to a diagnosis of malignancy when detected by imaging studies.


TERMINOLOGY


Abbreviations



  • Inflammatory pseudotumor-like follicular dendritic cell tumor (IPT-FDCT)


Synonyms



  • Terms inflammatory pseudotumor and inflammatory myofibroblastic tumor have been used as synonyms in the literature



    • This is confusing and may be incorrect


    • In this chapter these entities are distinguished


Definitions



  • IPT-FDCT is considered a variant of follicular dendritic cell sarcoma


  • Classification is controversial since several entities were previously lumped into category of splenic IPT



    • IPT-FDCT



      • True neoplasm of low malignant potential


      • Frequent association with Epstein-Barr virus (EBV)


      • Tends to involve spleen &/or liver


      • May overlap with EBV(+) cases without follicular dendritic cell markers


    • ALK(+) inflammatory myofibroblastic tumor (IMT)



      • Most often involves soft tissues of children and young adults


      • ˜ 50% of tumors have rearrangements at 2p23 involving anaplastic lymphoma kinase (ALK)


    • Splenic inflammatory pseudotumor (IPT)



      • Reactive process composed of admixed bland spindle cells and inflammatory cells


      • Probably results from multiple etiologies, including infections and repair


      • Benign lesions that do not recur after surgical excision


ETIOLOGY/PATHOGENESIS


Infectious Agents



  • Etiology is unknown


  • Strong association with Epstein-Barr virus



    • Epstein-Barr virus is monoclonal when assessed by EBV DNA terminal repeat regions


Cell of Origin



  • Spindled cells express 1 or more follicular dendritic cell markers


  • Spindled cells also can express focally smooth muscle actin or S100 protein


  • Cell of origin may be mesenchymal cell with differentiation along fibroblastic, myofibroblastic, or follicular dendritic cell lineages


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Uncommon; ˜ 1% of splenic tumors


    • Rare when compared with IPT at other sites of body


  • Age



    • Median: 44 years (range: 19-87 years)



      • Rare in children


  • Gender



    • Female predominance


Site



  • Appears in spleen as single lesion


Presentation



  • Affected patients are immunocompetent


  • Fever and weight loss in approximately 1/2 of patients


  • Epigastric or left flank pain in subset of patients



    • Splenomegaly may be noted in some cases


  • Can be incidental finding in asymptomatic patients




    • Lesion in spleen detected by radiologic imaging performed for other diseases


    • Imaging studies can demonstrate significant tumor growth in patients followed with less than 1 year intervals


Laboratory Tests



  • Usually unremarkable when not associated with other disease


Natural History



  • Cases of splenic IPT-FDCT appear to be closely related to liver IPT-FDCT



    • Histologically similar


    • Share association with EBV


  • More clinical information and follow-up are available for liver IPT-FDCT



    • Recurrences and metastases have been reported


    • Rare transformation of IPT-FDCT into overt follicular dendritic cell sarcoma


Treatment



  • Patients usually are diagnosed/treated with splenectomy



    • Due to rarity and nonspecific CT or MR imaging, these tumors are not diagnosed preoperatively


  • Symptoms and any laboratory abnormalities disappear after tumor resection


Prognosis



  • Good; no deaths attributable to IPT-FDCT of spleen


IMAGE FINDINGS


CT Findings



  • Discrete, single splenic mass and occasional splenomegaly


  • Lymphadenopathy is unusual


MACROSCOPIC FEATURES


General Features



  • Spleen weight: Ranges from 140-1,030 g


  • Well-circumscribed single mass



    • Cut surface is tan, gray, and firm; bulges in cross section



      • May have focal necrosis


    • Size: Ranges from 3-22 cm


MICROSCOPIC PATHOLOGY


Histologic Features



  • Well-demarcated tumor with occasional incomplete fibrous capsule


  • Loosely aggregated or dispersed oval or spindle cells admixed with abundant inflammatory cells



    • Spindled cells with moderate amount of pale to faintly eosinophilic cytoplasm



      • Oval vesicular nuclei with minimal atypia and distinct small nucleoli


    • Occasional small fascicles or focal storiform pattern


    • Rare mitotic figures


    • Occasional large cells with abundant cytoplasm and pleomorphic nuclei


  • Mixed inflammatory infiltrate of plasma cells, lymphocytes, and histiocytes



    • Lymphocytes are usually small admixed with occasional immunoblasts


    • Mature plasma cells with occasional Russell bodies


  • Other microscopic features



    • Focal necrosis with neutrophilic infiltrate


    • Histiocytes &/or eosinophils can be numerous


ANCILLARY TESTS


Immunohistochemistry



  • Spindled cells



    • Usually focal and weak reactivity with 1 or more follicular dendritic cell markers




      • CD21, CD35, CNA.42 (more frequent), and CD23 (less frequent)


      • More studies needed to establish frequency, pattern, intensity of expression of these markers


    • Vimentin(+), focal CD68(+), and focal smooth muscle actin(+/-)


    • Occasionally S100 protein ([+] focal)


    • EBV LMP1 occasionally (+)


    • Negative for CD15, CD30, CD34, EMA, and cytokeratin


    • HMB-45(-), ALK-1(-), HHV8(-)


  • Lymphocytes and plasma cells



    • T cells are usually more abundant than B cells


    • B cells and plasma cells are polytypic


In Situ Hybridization



  • Epstein-Barr virus encoded RNA (EBER)(+) in spindle cells in 40% of cases



    • Surrounding spleen is EBER(-) or degree of positive cells is significantly lower


Molecular Genetics



  • No evidence of monoclonal immunoglobulin or T-cell receptor gene rearrangements


  • EBV, when present, is monoclonal



    • Only a few cases have been studied


  • No known oncogene abnormalities


DIFFERENTIAL DIAGNOSIS

Tags:
Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Inflammatory Pseudotumor-like Follicular Dendritic Cell Tumor

Full access? Get Clinical Tree
Get Clinical Tree app for offline access