[489] Differential Expression of CK19, CD56 and CD57 in Neuroendocrine and Conventional Basal Cell Carcinoma: Is Neuroendocrine Basal Cell Carcinoma a Stand-Alone Entity?

George Jour, Thuy Nguyen, Debora Horton, Tatyana Isayeva, Aleodor Andea. SLR, NY; UAB, Bham

Background: Basal cell carcinoma (BCC) is the most common cutaneous neoplasm. Occasionally, Merkel cell carcinomas (MCC) display overlapping histologic features and may be confused with BCCs. Recently we have described a variant of BCC characterized by neuroendocrine (NE) histologic features (high N/C ratio, nuclear molding and a homogeneous chromatin pattern with inconspicuous nucleoli), increased mitotic rate and chromogranin positivity. We also found that Merkel cell polyomavirus (MCV) is frequently present in BCC with NE features. These findings raise the possibility of a potential link between NE BCCs and MCCs. Our study aims to further define NE BCC, on a spectrum ranging from classic BCC to MCC, by investigating expression of NE markers CD56 and CD57 and the stem cell marker CK19 which are commonly expressed in MCC.
Design: A total of 37 BCC cases were selected including 19 with NE morphology (defined as above) and 18 classic BCC. All cases were also evaluated for histologic pattern, mitotic index/ mm2, presence of apoptosis, necrosis, squamous differentiation, ulceration and peripheral palisading. Immunohistochemical stains for CK19, CD56, and CD57 were performed in all cases. Stain was considered positive when >10% of the cells labeled. Results for CK20, chromogranin and synaptophysin were available from a prior study.
Results: The immunohistochemical results in classic vs. NE BCCs are summarized below.

The expression of CD56 correlated with a lower mitotic rate (6 vs. 10 mitoses/ mm2 in CD56 positive vs. negative cases, respectively, p=0.05). There was no correlation between the other histologic features evaluated including histologic pattern, presence of apoptosis, necrosis, squamous differentiation, ulceration and peripheral palisading and status of the NE markers.
Conclusions: The expression rates of CK19, CD56 and CD57 are similar in NE and classic BCCs and much lower than in MCCs. These findings suggest that NE BCC has an “incomplete” neuroendocrine phenotype and is closer to classic BCC than to MCC. Yet, it differs from classic BCC by a higher rate of chromogranin expression and elevated mitotic rate and perhaps occupy an intermediate position between bona-fide cutaneous NE carcinomas and classic BCCs.
Category: Dermatopathology

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 113, Wednesday Afternoon


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