Lymph-Nodal Merkel Cell Carcinoma (MCC) in the Absence of Primary Tumor: Regression of the Primary or Lymph-Nodal Primitivity? Report of a Series with Favorable Prognostic Behavior.

Introduction: MCC is a rare cutaneous neuroendocrine neoplasm with aggressive behavior, a high recurrence rate and, generally, poor prognosis. Aim(s): To report histological and clinical features of a series of 12 patients with nodal MCC in the lack of evidence of a primary. Materials and methods: The cases were collected from a multicentric database: mean age at diagnosis was 67 yrs; F:M ratio was 1:1.4; mean follow-up was 54 months. Involved nodal sites were: inguinal (9) and axillar (3). All cases had typical MCC immunoprofile: neuroendocrine (CgA, NSE) and epithelial (CK 20 dot-like) marker positivity. Complete and extensive clinical, dermatologic, radiologic and endoscopic work-up was performed. M1 patients underwent surgery; in one case, chemotherapy, in another case biotherapy and in one further case, radiotherapy was administered. Results: All cases were in stage III of disease, according to UICC. All patients were alive without recurrence at the time of the study. The overall median survival was 52 months. The 4-yr survival was 100%. Conclusion: In patients with nodal metastases of MCC in the absence of a primary lesion, survival seems to be more similar to stage I rather than stage III, since 4-yr survival is reported about 60% for stage III disease in MCC. Regression of a small skin primary with nodal metastases or alternatively a primary nodal MCC might be hypothesized. In conclusion, the unknown primary nodal metastatic skin MCC seems to be associated with a more favorable prognosis. [ABSTRACT FROM AUTHOR]