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Frequent Positive Staining With NKI/C3 in Normal and Neoplastic Tissues Limits Its Usefulness in the Diagnosis of Cellular Neurothekeoma

Reena Sachdev, Uma N. Sundram MD, PhD
DOI: http://dx.doi.org/10.1309/3J3B7XVQF6CM0KTB 554-563 First published online: 1 October 2006


NKI/C3 originally was described as a marker for melanoma. Recently, it resurfaced as a marker to separate cellular neurothekeoma from other dermal tumors in the differential diagnosis. To determine the sensitivity and specificity of NKI/C3, we evaluated its staining pattern in 709 normal and neoplastic tissues, including 92 dermal tumors, using tissue microarrays and conventional sections. We found that although NKI/C3 is positive in only a few normal tissues, it stains a broad spectrum of neoplastic tissues. NKI/C3 is also positive in many dermal tumors of possible histiocytic origin, including juvenile xanthogranuloma (6/10), atypical fibroxanthoma (4/12), cellular fibrous histiocytoma (5/10), reticulohistiocytoma (3/6), and xanthoma (8/10). However, it is negative in epithelioid cell histiocytomas (0/7) and Langerhans cell histiocytosis (0/9). Given the wide spectrum of positive staining in morphologic mimics of cellular neurothekeomas, pathologists should be cautious when making this diagnosis based solely on positive staining with NKI/C3.

Key Words:
  • Cellular neurothekeoma
  • Immunohistochemistry
  • NKI/C3
  • Tissue microarray