Merkel cell carcinoma is rare in Chinese, but not to be overlooked

Abstract

Background: Merkel cell carcinoma (MCC), a primary neuroendocrine cancer of the skin, is increasing in incidence worldwide. The incidence of MCC in Chinese, particularly cases coexisting with other skin malignancies, was not widely reported. Aims: We aimed to study the clinicopathologic characteristics and outcomes of MCC in our patient population. Methods: Approximately 230,000 accessions between September 2012 and December 2020 were searched for MCC, basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and malignant melanoma (MM) in the pathology database. H&E and immunohistochemistry slides were reviewed and clinical information obtained for evaluation. Results & Conclusions: There were 291 primary skin cancers, including 191 BCC, 74 SCC, 24 MM and 2 cases of MCC, which account for only 0.69% of all skin cancers. Case 1 is a 58-year-old retired female with cutaneous SCC in-situ of face followed by identification of a combined/biphenotypic MCC and SCC in-situ (same location) found at excision, with microinvasion. At last annual follow-up 1 year after first diagnosis, she was alive with a solitary recurrent regional nodal metastasis of MCC. Case 2 is an 81-year-old retired male who presented with large left axillary nodal MCC (8 cm) for 1 year and a smaller (4 cm) left palm MCC for 9 months. He had metachronous BCC of right ring finger (resected 11 months ago) and SCC on left thigh (11 months ago), as well as histologically unconfirmed hepatic tumor (4 years earlier). He is currently alive without evidence of disease at 2 months after initial diagnosis. Neither patient received adjuvant therapy. Both cases showed typical morphological and immunohistochemical findings of MCC. Molecular studies were not performed. It is concluded that MCC is much rarer than other cutaneous malignancies and can occur synchronously or metachronously with other skin cancers.