MANCHESTER, ENGLAND — Patients with Merkel cell carcinoma are at high risk for multiple malignancies and should be closely examined at the time of diagnosis for other possible tumors, Dr. Julia K. Gass said at the annual meeting of the British Association of Dermatologists.
A review of the data of all 27 cases of Merkel cell carcinoma treated at Addenbrooke's Hospital National Health Service Trust, Cambridge, England, between 1995 and 2004 found additional tumors in 70% of cases, she said. The patients were elderly, with a mean age of 78 years. A total of 44% of these patients had one other tumor, 22% had three, and 4% had four additional malignancies.
Using information from the Eastern Region Cancer Registry, the rate of multiple malignancies was compared with that in the background population. When adjusted for advanced age, an incidence ratio of 3.47 was found, said Dr. Gass of Addenbrooke's dermatology department. Additional malignancies were cutaneous in 18 patients. Two of these were melanomas, seven were squamous cell carcinomas, and nine were basal cell.
An association of squamous cell carcinoma with Merkel cell carcinoma has been noted previously. Mixed tumors have also been seen, leading to the hypothesis that both types of tumor arise from a pluripotential epidermal stem cell damaged by ultraviolet light. Supporting the role of UV light in the pathogenesis of Merkel and squamous cell carcinomas is the finding that some of these tumors share UVB-type specific mutations of the p53 tumor suppressor gene and the Harvey-ras oncogene, she said.
The noncutaneous tumors in these patients included colorectal cancer in five, hematologic malignancies in three, and a breast tumor in one. The rare phenomenon of synchronous metastases from a Merkel cell carcinoma and from a second tumor to the same lymph node was seen in two patients, one with chronic lymphocytic leukemia and one with breast cancer. The synchronous metastasis of Merkel cell carcinomas and B-cell tumors, such as chronic lymphocytic leukemia, has previously been reported and may relate to genetic susceptibility, advanced age, immunosuppression by one tumor, or a common inducing agent.