Merkel cell carcinoma (MCC) is an uncommon tumor. Most clinical management recommendations in the literature are based on case series that describe a relatively small number of patients who were not entered on formal clinical trials, evaluated with uniform clinical staging procedures, treated with uniform treatment protocols, or provided with regular, prescribed follow-up. These reports are also confounded by potential selection bias, referral bias, and short follow-up; and they are underpowered to detect modest differences in outcome.
In addition, outcomes of patients with American Joint Committee on Cancer stage IA, stage IB, and stage II are often reported together. In the absence of results from clinical trials with prescribed work-up, treatments, and follow-up, most MCC patients have been treated using institutional or practitioner preferences that consider the specifics of each case as well as patient preference.
The histiocytic diseases in children and adults include three major classes of disorders of which only one, Langerhans cell histiocytosis (LCH), a dendritic cell disorder, will be discussed. Erdheim-Chester disease (primarily found in adults) and juvenile xanthogranuloma (diagnosed in children and adults) are macrophage disorders. Other disorders of the macrophage/monocytoid lineages include Rosai-Dorfman disease and hemophagocytic lymphohistiocytosis. Malignant disorders include malignant histiocytosis...
Two competing philosophies underlie many of the controversies about the most appropriate method of treating MCC. In the first philosophy, MCC is treated like other nonmelanomaskin cancers, with an emphasis on treating local-regional disease with surgery and radiation as appropriate. In the second philosophy, MCC is treated according to its "biologic features." This would make it analogous to small cell lungcancer, which is assumed to be a systemic disease, and would lead to a more routine recommendation of systematic adjuvant chemotherapy.
Surgery for the Primary Lesion
In a review of 18 case series, 279 of 926 patients (30.1%) developed local recurrence during follow-up, excluding those presenting with distant metastatic disease at presentation. These recurrences have been typically attributed to inadequate surgical margins or possibly a lack of adjuvant radiation therapy.[2,3]
Given the propensity of MCC to recur locally (sometimes with satellite lesions and/or in-transit metastases), wide local excision to reduce the risk of local recurrence has been recommended for patients with clinical stage I or stage II disease.
Recommendations about the optimal minimum width and depth of normal tissue margin that should be excised around the primary tumor differ among the various retrospective case series, but this question has not been studied systematically.[3,4,5,6,7][Level of evidence: 3iiiDiii] No definitive data suggest that extremely wide margins improve overall survival (OS), although some reports suggest that wider margins appear to improve local control.[Level of evidence: 3iiiDiii] Frozen-section evaluation of margins may be useful, especially when the tumor is in an anatomical site that is not amenable to wide margins.