Merkel cell carcinoma in situ: A systematic review of prognosis and management
December 10, 2021
The Australasian Journal of Dermatology
December 10, 2021
The vast majority of Merkel cell carcinomas are diagnosed at a time when the tumor involves the deeper layer of skin, the dermis. In less than 1% of cases, an early Merkel cell carcinoma tumor is found to only involve the upper layer of the skin, the epidermis. This is called “in situ“ Merkel cell carcinoma. These authors identified 27 cases of this rare variant across multiple large databases. The findings reinforce what we have always suspected about this unusual, early variant of MCC: it poses very little danger to patients. In situ MCC likely still needs to be treated carefully with surgery and some follow-up but clearly is a far less worrying subtype of this tricky cancer.
Background: Merkel cell carcinoma (MCC) is a rare primary cutaneous neuroendocrine tumour. While dermally invasive MCC is known to have a five-year survival of only 30-40%, the prognosis and management of MCC in situ (MCCis) is not widely reported.
Objective: We present a systematic review to elucidate the prognosis and management of MCCis.
Methods: We performed a systematic review, searching three databases to 01 June 2021. Case reports, cohort studies, clinical trials and literature reviews were considered for inclusion.
Results: We identified 26 cases of MCCis published in the literature with a median age of 74 years and involving 19 males and 7 females. Most cases were on the face and neck (n = 17), followed by upper limb (n = 8) and lower limb (n = 1). Sentinel lymph node biopsy was performed in three patients, and all were negative. One subject underwent adjuvant radiotherapy. No MCCis-associated deaths were reported.
Conclusion: This review suggests that MCCis has an excellent prognosis with minimal, if any, risk of mortality and a very low risk of dermal invasion and recurrence when treated with wide local excision alone. Sentinel lymph node biopsy is unlikely to be useful for MCCis.