[532] “Neuroendocrine” Basal Cell Carcinoma: A Novel Morphologic Variant?

R Patel, O Hameed, N Balmer, A Andea. University of Alabama at Birmingham, Birmingham, AL

Background: Basal cell carcinoma (BCC) is the most prevalent cutaneous neoplasm in the US. BCCs are usually composed of basaloid cells with hyperchromatic nuclei and relatively little cytoplasm. We have encountered few cases characterized by high nuclear to cytoplasmic ratio, nuclear molding and a homogeneous chromatin pattern with inconspicuous nucleoli reminiscent of neuroendocrine carcinoma. Immunohistochemical stains were negative for CK 20 ruling out Merkel cell carcinoma; however, the tumors expressed chromogranin. This observation prompted the current study which aims to evaluate the presence of “neuroendocrine“ features in BCCs.
Design: A total of 53 consecutive cases of aggressive and nodular BCC histologic variants were selected for the study. All cases were evaluated for histologic pattern, mitotic index/ mm2, presence of apoptosis, necrosis, squamous differentiation, ulceration and peripheral palisading. The presence of neuroendocrine (NE) morphology (high N/C ratio, nuclear molding, homogeneous chromatin pattern, inconspicuous nucleoli) was assessed by 3 separate investigators and a consensus was reached. In addition immunohistochemical stains for chromogranin, synaptophysin and CK20 were performed in all cases.
Results: NE morphology was noted at least focally in 50% of cases. CK 20 and synaptophysin were positive in 0% and 4% of cases, respectively. The differences in cases with NE versus without NE morphology are shown in the table.

In a multivariate analysis, high mitotic index and chromogranin positivity were independent predictors of NE morphology.
Conclusions: A neuroendocrine morphology in BCC is associated with expression of chromogranin, increased mitotic rate and prominent apoptosis. This group of BCCs appears to have an “incomplete” neuroendocrine phenotype as they are all negative for CK20 and only seldom express synaptophysin. Our study also is the first to document a relatively high frequency of chromogranin positivity in BCC tumors (52%). Further studies to assess the biological significance of NE phenotype are warranted.
Category: Dermatopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 90, Wednesday Afternoon


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