title: Human myxovirus resistance protein 1 (MxA) as a useful marker in the differential diagnosis of subcutaneous lymphoma vs. lupus erythematosus profundus.
abstract: BACKGROUND
  Substantial clinicohistologic overlap exists between lupus erythematosus profundus (LEP) and lymphomas involving the subcutis, including subcutaneous panniculitis-like T-cell lymphoma (SPTCL) and primary cutaneous gamma/delta T-cell lymphoma (GDTCL). Unequivocal markers separating the entities are not established.
  
  
  OBJECTIVE
  To explore the usefulness of interferon alpha (INF-α)-induced protein, myxovirus resistance protein 1 (MxA), in the differential diagnosis of these entities, as studies show that the expression pattern of MxA follows the distribution of the inflammatory infiltrate in cutaneous lupus, while INF- α is not known to operate in lymphoma.
  
  
  METHODS
  MxA immunohistochemistry was performed on skin biopsies from 5 patients with a clinical and histological diagnosis of SPTCL, 9 patients with GDTCL and 9 patients with LEP.
  
  
  RESULTS
  In SPTCL and GDTCL, MxA was primarily seen in macrophages and generally did not exceed 20% of the infiltrate. In contrast, a significant portion of the subcutaneous infiltrate was positive for MxA in LEP, with 50% of the infiltrate staining on average. A greater number of macrophages and lymphocytes stained with a greater intensity as well (P<0.001). Moreover, endothelial cell staining was uniquely identified in LEP but not in lymphoma.
  
  
  CONCLUSIONS
  Although specificity is not 100%, minimal staining of MxA is a predictor for SPTCL or GDTCL. Conversely, extensive staining for MxA both qualitatively and quantitatively is a feature of LEP. Endothelial staining also appears to be specific for LEP.
authors.affiliation: Department of Pathology and Laboratory Medicine, Room F-309, 1300 York Avenue, Weill Medical College of Cornell University, New York 10065, United States of America.
authors.forename: Xuan
authors.initials: X
authors.lastname: Wang
authors.forename: Cynthia M
authors.initials: CM
authors.lastname: Magro
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D003937:Diagnosis, Differential; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008214:Lymphocytes / Q000378:metabolism; D016399:Lymphoma, T-Cell / Q000175:diagnosis / Q000378:metabolism*; D016410:Lymphoma, T-Cell, Cutaneous / Q000175:diagnosis / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D064547:Myxovirus Resistance Proteins; D015434:Panniculitis / Q000175:diagnosis / Q000378:metabolism*; D015435:Panniculitis, Lupus Erythematosus / Q000175:diagnosis / Q000378:metabolism*; D012878:Skin Neoplasms / Q000175:diagnosis / Q000378:metabolism*
chemical_list: D015415:Biomarkers; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; D019204:GTP-Binding Proteins