Microscopical synopsis

 erythrophagocytic histiocytosis (#12747473#)

Immunochemistry

 CD68 +
 lysozyme +
 alpha-1-antitrypsin +
 CD45 +
 CD45RO +
 CD1a +
 S-100 - or + (#9808131#, #12747473#)

References

 Hornick JL, Jaffe ES, Fletcher CD. Extranodal histiocytic sarcoma: clinicopathologic analysis of 14 cases of a rare epithelioid malignancy. Am J Surg Pathol. 2004 Sep;28(9):1133-44. PMID: #15316312#

 Copie-Bergman C, Wotherspoon AC, Norton AJ, Diss TC, Isaacson PG. True histiocytic lymphoma: a morphologic, immunohistochemical, and molecular genetic study of 13 cases. Am J Surg Pathol. 1998 Nov;22(11):1386-92. PMID: #9808131#