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. 2025 Jan 22;36(1):1.
doi: 10.1007/s12022-024-09845-w.

Evaluating CK20 and MCPyV Antibody Clones in Diagnosing Merkel Cell Carcinoma

Begum Yeni Erdem  1 , Can Baykal  2 , Yasemin Ozluk  1 , Melin A Ahmed  3 , Erol Kozanoglu  4 , Pinar Saip  3 , Nesimi Buyukbabani  1   5 , Sule Ozturk Sari  6
Affiliations

Evaluating CK20 and MCPyV Antibody Clones in Diagnosing Merkel Cell Carcinoma

Begum Yeni Erdem et al. Endocr Pathol. .

Abstract

Merkel cell carcinoma (MCC) is diagnosed through histopathological and immunohistochemical examination of biopsies from skin or other organs. Its distinguishing features include perinuclear dot-like staining with Cytokeratin 20 (CK20) and detection of Merkel cell polyomavirus (MCPyV) using various methods. However, CK20 and MCPyV negative MCC cases have been reported at varying rates. In this single center cross-sectional study, we aimed to determine which clones are more effective in diagnosing MCC by comparing the performance of CK20 antibody clones Ks20.8 and SP33, as well as MCPyV antibody clones Ab3 and CM2B4. Fifty-four patients diagnosed with MCC were included. Among these, 42 cases were primary cutaneous, and 12 cases were nodal MCC. Fifty-two (96.3%) cases were positive with both CK20 clones, while two cases were negative. Clone SP33 stained areas of necrosis, whereas Ks20.8 showed no aberrant staining. MCPyV was detected in 44 cases (81.5%) using clone Ab3 and 39 cases (72.2%) using clone CM2B4. Staining with MCPyV clone Ab3 was diffuse and strong in most cases, while approximately 30% of CM2B4-positive cases exhibited low percentages and/or weak staining, complicating the evaluation. The two CK20-negative cases were also negative with both MCPyV clones. Our data demonstrated that CK20 clone Ks20.8 may be preferred for MCC diagnosis due to its consistent performance and lack of aberrant staining. Similarly, MCPyV clone Ab3 appears superior to CM2B4 for identifying MCPyV-positive cases.

Keywords: Clone Ab3; Clone CM2B4; Cytokeratin 20; Merkel cell carcinoma; Merkel cell polyomavirus.

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Conflict of interest statement

Declarations. Ethics Approval: The study was approved by the Institutional Review Board at Istanbul Faculty of Medicine, Istanbul University. Competing Interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Histopathological findings: A and C Bowen disease over MCC; B Round shaped cells with narrow cytoplasm; D Anastomosing and irregular trabecular configuration of tumor cells with open chromatin
Fig. 2
Fig. 2
Staining patterns of two clones of CK20 antibody in the same cases: A-B Staining in necrosis (inlet: H&E; circles: areas of necrosis; A Ks20.8; B SP33); C-D Differences in intensity (C Ks20.8 stronger; D SP33 weak)
Fig. 3
Fig. 3
Staining patterns of two clones of MCPyV antibody in the same cases: A Ab3 (+); B CM2B4 (-) (Cytoplasmic reaction); C Ab3 (+); D CM2B4 (+) but focal; E Ab3 (+); F CM2B4 (+) but weak
Fig. 4
Fig. 4
Distribution of primary tumors on a body figure according to MCPyV clone Ab3
See this image and copyright information in PMC

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