Clinical behavior and prognosis of lymph-nodal Merkel cell carcinoma (MCC) in the absence of a primary tumor.

Abstract

e19038 Background: MCC is a rare cutaneous neuroendocrine neoplasm characterized by an aggressive behavior and a high recurrence rate, generally associated with poor prognosis. Nodal and distant metastases are frequent. Aim of this study was to report histological, clinical and prognostic features of a series of 12 patients with nodal MCC in the lack of evidence of a primary. Methods: The cases were collected from a multicentric database: mean age at diagnosis was 67 years; F:M ratio was 1:1.4; mean follow up was 54 months (8-108). Involved nodal sites were: inguinal (9) and axillar (3). All cases had typical MCC immunoprofile: neuroendocrine (CgA, NSE, Syn) and epithelial (CK 20 dot-like) marker positivity. Complete and extensive clinical, dermatologic, radiologic and endoscopic work-up was performed. All patients underwent surgical excision; 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 AJCC. All patients were alive without recurrence at the time of the study. The overall mean survival was 52 months. The 4-yr survival was 100%. Conclusions: 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. This finding must still be completely explained. 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.