Clinical mnemonic for MCC MERKEL CELL CARCINOMA

A recent study presented a mnemonic for the clinical features associated with Merkel cell carcinoma:AEIOU. This study found that 89% of 62 Merkel cell carcinoma cases exhibited at least three of the five features listed below. If a lesion exhibits at least three of these features, suspicion of MCC should increase and biopsy be considered. In particular, a lesion that is red or purple, rapidly growing, but non-tender should be of concern.

Asymptomatic/non-tender: 88%

Expanding rapidly: 63%

Immune suppressed: 8%

Over age 50: 90%

Ultraviolet light exposed site: 81%

In January of 2008, a new polyomavirus was reported to be present in MCC tumors. This virus, named the Merkel cell polyomavirus (abbreviated MCV or MCPyV) was discovered by extensive sequencing of MCC tumor RNA. Initially, MCPyV DNA was reported to be present in 8 of 10 MCC tumors as compared to only 1 of 15 skin controls. This strong association of the virus with MCC has been confirmed by numerous other studies that in aggregate have now found MCPyV to be present in a much greater percentage of MCCs than basal cell carcinomas, squamous cell carcinomas, melanomas, or normal skin samples.

Lymphovascular invasion and growth pattern hold prognostic significance Merkel cell carcinoma

Lymphovascular invasion (LVI) was associated with poorer outcome. Presence of LVI was defined by tumor emboli within vascular spaces outside the tumor boundary, as visible on a standard hematoxylin/eosin stained slide. Persons with MCC tumors with detectable LVI had a worse overall survival as compared to those with tumors without LVI (71% vs. 98% survival at 2 years, p<0.001).

An infiltrative tumor growth pattern was associated with poor outcomes as compared to MCC tumors with a nodular growth pattern. Well-circumscribed tumors were considered “nodular” and those with rows, trabeculae, or single cells penetrating the dermis deemed “infiltrative”; tumors that exhibited both features were considered “infiltrative.” 2-year survival for MCCs with an infiltrative pattern was 72% as compared to 93% for well-circumscribed tumors.

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