53 yrs female with history/diagnosis of autoimmune throbocytopenic purpura.  
2013 threpine: reactive changes, probably induced peripheral hemato-cell consumption.  
2014 splenomegaly (laparoscopic) performed.  
MACRO: >50 spleen fragments from 0,5x0,5x0,3 cm up to 9,5x5x3,5 cm. Multiple brown elastic nodules up to iki 2,5x2x2 cm in the sections.  
HISTO: Multinodular infiltrating proliferation of highly atypical histiocytes with pleomorfphic, lobated nuclei and microvesiculated cytoplasm. Scattered megakariocytes with pleomorphic hyperchromatic nuclei and islands of erythroblasts with Ki67+ activity within infiltrate.  
IH: CD4+; CD68+;Lysozyme+; CD1a/S100(-); CD23/CD21(-). Ki67 prolif. activity low <5% (mainly higher on erythros, scattered histiocytic nuclei).  
OF NOTE: We have not more Ma markers there, I'm very sorry.  
 
Proposal: Histiocytic tumor/sarcoma with extramedullary haematopoiesis and hemophagocytosis.  
Question: Low Ki67 activity? Probablity of reactive changes?  
Dif. dx: Tumoral extranodal haemophagocytosis with prominent atypical histiocytic reaction. EXAMPLE OF THIS PATHOLOGY: http://www.ipath-network.com/ltpatho/object/view/372150  
 
Pubmed search:  
1. Primary splenic histiocytic sarcoma complicated with prolonged idiopathic thrombocytopenia and secondary bone marrow involvement: a unique surgical case presenting with splenomegaly but non-nodular lesions.  
Yamada S, Tasaki T, Satoh N et al. Diagn Pathol. 2012 Oct 17;7:143. doi: 10.1186/1746-1596-7-143. PMID: 23075171  
2. Oka K1, Nakamine H, Maeda K et al. Primary histiocytic sarcoma of the spleen associated with hemophagocytosis. Int J Hematol. 2008 May;87(4):405-9. doi: 10.1007/s12185-008-0059-6.