[494] BerEp4, Cytokeratin 17, and Cytokeratin 14 Immunohistochemical Staining Aid in Differentiatation of Basaloid Squamous Cell Carcinoma from Basal Cell Carcinoma with Squamous Features

Devon C Gimbel, Katy R Linskey, Lawrence Zukerberg, Lyn M Duncan, Peter M Sadow, Rosalynn M Nazarian. Masachusetts General Hospital, Boston

Background: Basaloid squamous cell carcinoma (BSCC) is an uncommon variant of squamous cell carcinoma which may histologically overlap with basal cell carcinoma (BCC) with squamous metaplasia. Differentiating between these neoplasms is important because of the worse prognosis associated with BSCC and the importance in determining the nature of basaloid metastases of unknown primary. BerEp4 immunohistochemical staining can help distinguish conventional primary cutaneous BCC and BSCC, but is of limited utility in BCC with squamous differentiation, prompting the need to identify additional biomarkers to help distinguish these entities.
Design: We investigated BerEp4, Cytokeratin 17 (CK17) and Cytokeratin 14 (CK14) immunohistochemical staining in basaloid squamous cell carcinoma (n=15, with 5 cutaneous and 10 aerodigestive tract BSCC, including 3 lymph node metastases) and cutaneous basal cell carcinoma with squamous features (n=15). The percentage of tumor cells staining with these immunohistochemical markers was scored as 0 (none), 1 (<10% focal), 2 (10-80% patchy) and 3 (>80%diffuse positivity).
Results: The mean percentage of staining for all markers was significantly higher in the BCC with squamous differentiation group compared to the BSCC group (P=0.002 for BerEp4, P=0.0001 for CK17, P=0.0001 for CK14; unpaired t test). 80% (12/15) BCC displayed diffuse staining for all markers; 0% (0/15) of BSCC cases had diffuse staining for all three markers. While diffuse BerEp4 staining was observed in 3 BSCC cases, only focal or patchy/peripheral rim staining for CK14 and CK17 was present. The pattern of staining and % of positive cells are important to evaluate, rather than scoring as "positive" or "negative". To test the utility of this protocol, three additional cases of basaloid carcinoma of unknown primary metastatic to neck lymph nodes were stained. These tumors stained similarly to the basaloid squamous cell carcinomas with lack of diffuse positivity for all three markers. Five cases of p16 positive mucosal (anal canal) BSCC's showed a score or 0 or 1 for BerEp4 and 2 or 3 for CK14 and CK17 (p<0.001).
Conclusions: An immunohistochemical panel composed of BerEp4, CK14 and CK17 is useful for differentiating primary cutaneous BCC and metastatic basaloid-type tumors of the oropharynx and anus. This panel can be employed to better classify basaloid tumors with an aim towards guiding appropriate patient management.
Category: Dermatopathology

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 128, Wednesday Afternoon


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