TORONTO Ulceration and depth of invasion should be included in the staging of Merkel cell cancers, as they are for the staging of melanoma, because of the strong similarities between the two types of neoplasm, Dr. Ralph L. George and Dr. A. McGuire said in a poster presented at the annual meeting of the Canadian Association of Thoracic Surgeons.
As with melanoma, ulceration in a primary Merkel cell cancer appears to be an indication that the tumor has spread.
An analysis of 14 Merkel cell cancer cases found that ulceration was significantly associated with metastatic disease. Depth of invasion was also a sign of advanced disease that "approached but did not achieve statistical significance," Dr. George said in an interview.
Merkel cell cancer is a rare form of cutaneous neuroendocrine neoplasm that is known to have a poor prognosis, but there is limited information on staging Merkel cell cancer and no data on the prognostic significance of ulceration, wrote Dr. George and Dr. McGuire of Kingston (Ont.) Regional Cancer Centre, Queen's University.
After noticing that patients coming to their clinic with either of the cancers had the same risk factors, the physicians decided to compare the prognostic and etiologic characteristics of 232 melanoma cases with those of the Merkel cases.
They documented several important similarities. Like melanoma, Merkel cell cancer was most common in type I, II, and III skin and on sun-exposed areas of the body. In fact, Merkel cell cancer's relationship with sun exposure was "even stronger than that of the melanomas, with a P value equal to .026 for the comparison," Dr. George said.
Like melanoma, Merkel cell cancer occurred more in older patients and showed a propensity for full-thickness skin invasion, metastases to regional lymph nodes, and systemic failure.
These data are preliminary and need to be confirmed in a larger study. "Knowing about the staging [may] lead to better treatment. We have systemic treatment for melanoma but we do not have … an effective systemic treatment for Merkel at this time. If we can predict a group who are likely to fail, we can perhaps target them with adjuvant therapy," Dr. George said.