Background The morpheaform subtype of basal cell carcinoma (BCC) often presents a diagnostic histological challenge, and its true margin may be difficult to determine with accuracy. This tumor may also be difficult to distinguish from other adnexal neoplasms having a benign clinical course. Previous work has shown that cytokeratin 17 (K17) expression is increased in BCC. Objective To confirm the expression of K17 across the subtypes of superficial, nodular and morpheaform BCC variants. Secondly, compare K17 expression in each of these subtypes of BCC to two other adnexal neoplasms. Methods Tissue specimens from each tumor category were randomly collected, immunolabeled, and scored for K17 expression by intensity and extent of immunostaining. Results Our results indicate that K17 is a very useful marker in the identification and outlining of BCC. Moreover, in morpheaform BCC, K17 immunostaining clearly detected individual tumor cells well away from the dermal tumor strands that otherwise seemed non-malignant by hematoxylin and eosin staining alone. In addition, we report that the expression of K17 in morpheaform BCC is capable (100% of specimens; p<0.0001) of distinguishing this tumor from desmoplastic trichoepithelioma. Conclusion We propose that K17 immunostaining could improve the diagnostic and surgical management of these tumors.

Intravascular invasion of tumor cells can be associated with metastasis in many cancers. Basal cell carcinomas (BCCs), however, rarely metastasize; therefore, the clinical impact of intravascularly invasive BCC (IVBCC) is currently unclear. Because of these facts and the rarity of IVBCC, questions have arisen on whether IVBCC truly exists. We present 4 cases of IVBCC: one case with obvious tumor islands within immunolabeled blood vessels in the context of advanced disease and 3 cases found incidentally during Mohs micrographic surgery. We discuss the difficulty in studying IVBCC, the idea that it could be due to artifact, and the lack of direct clinical-pathological correlation. Given these challenges, we propose diagnostic criteria for IVBCC to decrease ambiguity for pathological diagnosis. Such criteria may facilitate further studies on the clinical significance of IVBCC.