LN-2 (CD74). A marker to distinguish atypical fibroxanthoma from malignant fibrous histiocytoma.
BACKGROUND
In this study, the authors examined the expression of LN-2, an antigen expressed by B cells, macrophages, and Reed-Sternberg cells, in a variety of spindle cell lesions of the skin to determine whether LN-2 immunoreactivity can be used to differentiate among these tumors. For comparison, they examined CD34 antigen expression in these lesions, which has been shown to be a useful marker in differentiating dermatofibrosarcoma protuberans from dermatofibroma.


METHODS
Immunocytochemistry with anti-LN-2 and anti-CD34 monoclonal antibodies on formalin fixed, paraffin embedded material was performed on 102 spindle cell lesions, including dermatofibroma, dermatofibrosarcoma protuberans, atypical fibroxanthoma, malignant fibrous histiocytoma, leiomyoma, and neurofibroma.


RESULTS
LN-2 immunoreactivity did not distinguish between dermatofibroma and dermatofibrosarcoma protuberans, both of which showed weak immunoreactivity. In marked contrast, 90% of cases of malignant fibrous histiocytoma showed strong staining for LN-2, whereas the vast majority (90%) of cases of atypical fibroxanthoma were negative or stained only weakly with anti-LN-2 antibodies. Of the two cases of atypical fibroxanthoma that stained strongly for LN-2, both lesions were > 2 cm in size and extended deep into the subcutaneous fat.


CONCLUSIONS
Differential expression of the LN-2 antigen by atypical fibroxanthoma and malignant fibrous histiocytoma distinguishes these two lesions and suggests that acquisition of LN-2 positivity may be a marker of tumor progression.
Lazova
R
R
Department of Pathology, University of Rochester Medical Center, New York 14642, USA.
Moynes
R
R
May
D
D
Scott
G
G
D000911:Antibodies, Monoclonal; D018952:Antigens, CD34 / Q000032:analysis / Q000276:immunology; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis* / Q000276:immunology; D014408:Biomarkers, Tumor / Q000032:analysis*; D004396:Coloring Agents; D018223:Dermatofibrosarcoma / Q000473:pathology; D003937:Diagnosis, Differential; D018219:Histiocytoma, Benign Fibrous / Q000473:pathology*; D000949:Histocompatibility Antigens Class II / Q000032:analysis* / Q000276:immunology; D006801:Humans; D007150:Immunohistochemistry; D012878:Skin Neoplasms / Q000473:pathology
D000911:Antibodies, Monoclonal; D018952:Antigens, CD34; D000944:Antigens, Differentiation, B-Lymphocyte; D014408:Biomarkers, Tumor; D004396:Coloring Agents; D000949:Histocompatibility Antigens Class II; C045084:invariant chain