Epithelioid sarcoma: an immunohistochemical analysis evaluating the utility of cytokeratin 5/6 in distinguishing superficial epithelioid sarcoma from spindled squamous cell carcinoma.
BACKGROUND
Epithelioid sarcoma (ES) is a rare, aggressive soft tissue tumor characterized by nodular aggregates of epithelioid and/or spindled cells that are immunoreactive to cytokeratins (CKs) and epithelial membrane antigen. ES that arises in the dermis may cause epidermal ulceration and can resemble, clinically, morphologically and immunohistochemically, cutaneous squamous cell carcinoma. CK 5/6 has recently been found to be an excellent marker of squamous cell carcinoma, including spindled variants, but it is not known if this marker can be utilized to distinguish superficial ES from cutaneous spindled squamous cell carcinoma (SSCC).


METHODS
Twenty-four cases of ES with typical histologic features and 10 cases of SSCC with ultrastructural evidence of epithelial differentiation were studied. Immunohistochemical analysis using an antibody to CK 5/6 was performed. The extent of immunoreactivity was evaluated in a semiquantitative manner using the following scale: 0, < 5% of cells staining; 1+, 6-25% of cells staining; 2+, 26-50% of cells staining; 3+, 51-75% of cells staining; 4+, > 75% of cells staining.


RESULTS
CK 5/6 was expressed in all 10 cases of SSCC, including one case with 3+ staining and six cases with 4+ staining. In contrast, CK 5/6 staining was found only in rare tumor cells (1+ staining) in one of 24 (4%) cases of ES.


CONCLUSIONS
CK 5/6 staining is useful in distinguishing superficial ES from cutaneous SSCC.
Lin
Lin
L
Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Skacel
Marek
M
Sigel
Jessica E
JE
Bergfeld
Wilma F
WF
Montgomery
Elizabeth
E
Fisher
Cyril
C
Goldblum
John R
JR
D014408:Biomarkers, Tumor / Q000032:analysis*; D002277:Carcinoma / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000473:pathology; D003937:Diagnosis, Differential; D006801:Humans; D007150:Immunohistochemistry; D053555:Keratin-5; D007633:Keratins / Q000032:analysis / Q000096:biosynthesis*; D012509:Sarcoma / Q000378:metabolism* / Q000473:pathology; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology
D014408:Biomarkers, Tumor; C503940:KRT5 protein, human; D053555:Keratin-5; D007633:Keratins