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Published on: July 9, 2014
The diagnostic utility of Merkel cell polyoma virus immunohistochemistry in cytology specimens
Aysha Mubeen1,2, Jeffrey K Mito1
1Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts, USA.
Objective:
Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine neoplasm that predominantly affects elderly and immunocompromised patients. Merkel cell polyoma virus (MCPyV) is clonally integrated into the majority of MCCs and has been linked to patient outcomes, playing a central role in the pathogenesis of the disease. We aimed to assess the utility of MCPyV immunohistochemistry (IHC) in the diagnosis of MCC in cytology cell block specimens and correlating with clinicopathologic features.
Methods:
Fifty-three cytology samples of MCC with sufficient cell block material were stained for MCPyV by IHC and scored semi-quantitatively in extent and intensity. Morphologic mimics of MCC including small cell lung carcinoma (n = 10), non-Hodgkin lymphoma (n = 10), basaloid squamous cell carcinoma (n = 6) and other neuroendocrine carcinomas (n = 8) were stained in parallel. Positive staining was defined as >1% of the tumour cells showing at least moderate staining intensity.
Results:
The cytologic features of MCC were characterized by high nuclear-cytoplasmic ratios, hyperchromatic nuclei with 'salt and pepper' chromatin, and nuclear moulding. MCPyV was detected in 24 of 53 cases (45%). Staining was strong and diffuse in roughly half of the positive samples. Of the morphologic mimics, one follicular lymphoma showed strong and diffuse staining. In contrast to prior studies, we saw no association between MCPyV status and patient outcomes.
Conclusion:
Merkel cell polyoma virus IHC is highly specific (97%) for the diagnosis of MCC in our cohort, and can serve as a useful diagnostic tool for distinguishing MCC for morphologic mimics.
Insights
Merkel cell polyoma virus (MCPyV) immunohistochemistry (IHC) shows high specificity for diagnosing Merkel cell carcinoma (MCC) in cytology samples. This diagnostic tool aids in differentiating MCC from similar-looking tumors.
Area of Science:
- Oncology
- Virology
- Pathology
Background:
- Merkel cell carcinoma (MCC) is an aggressive skin cancer predominantly affecting elderly and immunocompromised individuals.
- Merkel cell polyoma virus (MCPyV) is implicated in MCC pathogenesis and has been linked to patient outcomes.
Purpose of the Study:
- To evaluate the diagnostic utility of MCPyV immunohistochemistry (IHC) in MCC cytology cell block specimens.
- To correlate MCPyV IHC findings with clinicopathologic features of MCC.
Main Methods:
- Fifty-three MCC cytology samples were stained for MCPyV using IHC and scored semi-quantitatively.
- Morphologic mimics of MCC, including small cell lung carcinoma and lymphomas, were also stained for MCPyV.
- Positive staining was defined as >1% of tumor cells exhibiting moderate to strong intensity.
Main Results:
- MCPyV was detected in 45% (24/53) of MCC cases, with staining often strong and diffuse.
- One case of follicular lymphoma showed strong and diffuse MCPyV staining among the mimics.
- No association was found between MCPyV status and patient outcomes in this cohort.
Conclusions:
- MCPyV IHC demonstrates high specificity (97%) for diagnosing MCC in cytology cell blocks.
- MCPyV IHC is a valuable tool for distinguishing MCC from morphologic mimics in cytological specimens.
