74 yrs female presenting with enlarged lateral neck lymph nodes up to 5cm. All 3 biopsies (large nodes) shows the same changes- named as "reactive".  
HISTORY: previous resection of goiter.  
HISTO: Vaguelly nodular spindle cell/histiocytic proliferation in the node with admixture of polytypic plasmacytes/lymhocytes. Peripheral lymph node architecture is blurred with residual follicles with focally prominent marginal zones and nodule forming in MZ projection/ interfollicular space. Any definitelly LYMPHOPROLIFERATION is visible, except histiocytic nodules. Focal cellular accumulation of atypical cells with large vesiculated nuclei (as in IMFT) and multilobated nuclei in some nodules present. Mitoses up to 2/10 DPRL.  
IH: Spindle cells CD23/CD21/S100/D2-40/EMA/PanCK/Desmin/Asm Actin/MelanA(-), ALK1 (new sensitive for lung AC) CD68/Lysozyme (?)(single cells +?); LCA/HLA-DR(-)(?)(mainly multiple small-medium spindle macrofages +); CD43(-); INI1+; In part FXIIIa+... Ki67 index low.  
GIant cells: clearly CD68+LCA+.  
IgG4/IgG ratio not so prominent.  
MOLECS: IGH ir IGK polyclonal. NOTE: IGH FR1 slightly atypical profile (small clone?), but formally (quantitativelly) negative.  
TCRB ir TCRG polyclonal.  
EBER and additional (deeper) IH: pending.  
PHOTOS: multiple blocks- the last digit means block number.  
TECHNO NOTE: parafin blocks are suboptimal quality: ih stains flow out...  
 
PROPOSAL/DIFFERENTIAL: a) low grade mesenchymal/fibroblastic dendritic neoplasia, probably (fibroblastic reticular) dendritic cell sarcoma/tumor with "O" phenotype? Or just IMFT- metastatic vs primary(?);  
b) B marginal zone lymphoma with exuberrant histiocytic/fibroblastic/dendritic(?) proliferation or IgG4 disease?  
REALLY I feel missing something else...