Datasets
This dataset has been developed for the reporting of the pathologic findings of primary cutaneous Merkel cell carcinoma (MCC) in excision (resection) specimens containing tumour. This dataset does not apply to partial superficial biopsies or re-excisions with no residual primary tumour. It is also not applicable for cytology specimens.
For small partial biopsies and cytology specimens, reporting the tumour diagnosis is usually sufficient. If there is no residual tumour seen in a re-excision, this should be reported. The features of the tumour seen in prior biopsies or excisions do not need to be repeated. In situations in which an initial partial (incisional or excisional) biopsy contains a substantial amount of tumour, completion of the dataset may require synthesising the findings of both the biopsy and subsequent excision with residual tumour.
A separate ICCR dataset is available for reporting invasive melanoma.
2nd edition – January 2026
Updated following the publication of the 2025 World Health Organization (WHO) Classification of Skin Tumours, 5th edition.
This 2nd edition dataset was developed with the kind support of the International Melanoma Pathology Study Group (IMPSG).
SUMMARY OF CHANGES
• Updated to Union for International Cancer Control TNM9 staging, including errata published October 2025.
• Revised guide to harmonise with ICCR style for element titles and value list.
• Added new core element ‘Clinical information’.
• Added new core element ‘Specimen(s) submitted’.
• Renamed ‘Anatomic site’ to ‘Tumour site’.
• Added new non-core element ‘Block identification key’.
• Renamed ‘Tumour size’ to ‘Tumour dimensions’.
• Renamed and reordered ‘Morphological diversity’ to ‘Histological tumour type’.
• Renamed ‘Locoregional cutaneous metastases’ to ‘Non-nodal locoregional cutaneous metastases’.
• Added new non-core element ‘Histological growth pattern’.
• Renamed ‘Immunohistochemistry’ to ‘Ancillary studies’ and included ‘Representative blocks for ancillary studies’.
• Other minor updates to elements were also included.
• Revised all notes, including incorporation of the 2025 WHO Classification of Skin Tumours, 5th edition.
1st edition – December 2019
The 2nd edition of the dataset for Merkel cell carcinoma was developed by the following international team:
Domain experts:
Authors of previous edition of this dataset are available here.
