Diagnostic utility of cytokeratin 17 immunostaining in morpheaform basal cell carcinoma and for facilitating the detection of tumor cells at the surgical margins

Abstract

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 (CK17 or K17) expression is high in BCC.

Objective: To confirm the expression of K17 across the subtypes of superficial, nodular and morpheaform BCC variants and to compare K17 expression in each of these subtypes of BCC with that in two other adnexal neoplasms.

Methods: Tissue specimens from each tumor category were randomly collected, immunolabeled, and scored for K17 expression according to intensity and extent of immunostaining.

Results: Our results indicate that K17 is a 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 nonmalignant according to hematoxylin and eosin staining alone. In addition, the expression of K17 in morpheaform BCC is capable (100% of specimens; p < .001) of distinguishing this tumor from desmoplastic trichoepithelioma.

Conclusion: We propose that K17 immunostaining could improve the diagnostic and surgical management of these tumors.

Figure 1. Cytokeratin 17 is intensively expressed in different sub-types of basal cell carcinoma (BCC)

a) Routine H&E stained superficial BCC showing basaloid nodules extending into the superficial dermis. 10X. b) K17 immunostaining of superficial BCC, showing diffuse expression throughout the tumor. 10X. c) Routine H&E stained nodular BCC, showing large nodules of basaloid cells in the dermis. 10X. d) K17 immunostaining of nodular BCC, showing diffuse expression throughout the tumor. 10X.

Figure 2. Cytokeratin 17 expression highlights morpheaform basal cell carcinoma (BCC)

a) Routine H&E staining of morpheaform BCC showing basaloid strand of cells in a sclerosing dermal stroma. 10X. b) K17 immunostaining of morpheaform BCC, showing diffuse expression throughout the tumor strands. 10X. c) Routine H&E staining of morpheaform BCC, showing scattered basaloid strands and small islands of tumor within the dermis. 4X. d) K17 immunostaining highlights the tumor strands and islands. 4X. e) Higher magnification of a portion of panel “d”, showing individual tumor cells (arrows) away from the tumor strands. 40X.

Figure 3. Cytokeratin 17 expression highlights a larger tumor of morpheaform basal cell carcinoma (BCC) and its margins

a) Routine H&E staining of morpheaform BCC, showing basaloid strands of tumor cells in a sclerosing dermal stroma. 10X. b) K17 immunostaining of morpheaform BCC, showing diffuse expression throughout the tumor strands. 10X. c) Higher magnification of a portion of panel “a”, showing scattered basaloid strands within the dermis. 40X. d) Higher magnification of a portion of panel “b”, at its margin, showing K17 immunostaining highlighting the tumor strands and individual neoplastic cells (arrows). 40X. (copyrighted, V. Falanga, 2011).

Figure 4. Cytokeratin 17 expression can distinguish morpheaform basal cell carcinoma (BCC) from desmoplastic trichoepithelioma (DT)

a) Routine H&E staining of desmoplastic trichoepithelioma, showing small basaloid strands and horn pseudocysts within a fibrotic stroma. 4X. b) K17 immunostained DT, showing absence of K17 expression in the basaloid strands comprising the tumor. 4X. c) Routine H&E staining of DT showing small basaloid strands and horn pseudocysts within a fibrotic stroma. 4X. d) K17 immunostained DT, showing absent K17 expression in basaloid strands. There is some nonspecific immunostaining of the horn pseudocysts within the lesion. 4X. e) Higher magnification of a portion of panel “d”, highlighting the absence of K17 expression in the basaloid strands of this DT section (arrows). 40X.

Figure 5. Cytokeratin 17 expression in frozen section of morpheaform basal cell carcinoma (BCC)

The photomicrograph shows distinct expression of cytokeratin 17 in a BCC tumor, including dermal cords and strands. 4X.