Unknown primary Merkel cell carcinoma: 23 new cases and a review.

BACKGROUND: Knowledge is limited regarding unknown primary Merkel cell carcinoma (UPMCC). OBJECTIVE: We sought to document the characteristics and behavior of UPMCC, and determine the most appropriate treatment. METHODS: A multicenter, retrospective, consecutive study reviewing patients given a diagnosis of UPMCC between 1981 and 2008 was completed. In addition, a literature review of cases of UPMCC was performed. RESULTS: In all, 23 patients with UPMCC are described and 34 cases from previous reports are compiled. Among the 23 new cases of UPMCC, the average age at diagnosis was 66.0 years; the majority of patients were male (87%) and Caucasian (100% of those reported). One patient was immunosuppressed, and 39% had a history of other cancer. After the initial biopsy, 16 patients had further evaluation of the involved lymph node basin. Half of these had additional positive nodes (8 of 16). The majority of patients had lymph node basin involvement only (78%), whereas 22% had lymph node basin and distant metastasis. The most common lymph node basin involved was inguinal. The median size of the involved lymph node at diagnosis was 5.0 cm. At 2 years, the overall survival of stage IIIB UPMCC was significantly improved versus stage IIIB known primary Merkel cell carcinoma (MCC): 76.9% to 36.4%. LIMITATIONS: Limited number of cases and retrospective review are limitations. CONCLUSION: Our data demonstrate improved overall survival in patients with stage IIIB UPMCC versus those with stage IIIB known primary MCC. Because of the unpredictable natural history of UPMCC, we recommend individualization of care based on the details of each patient's clinical presentation.

Prognostic factors in Merkel cell carcinoma: analysis of 240 cases.

BACKGROUND: Knowledge regarding behavior of and prognostic factors for Merkel cell carcinoma (MCC) is limited. OBJECTIVE: We sought to further understand the characteristics, behavior, prognostic factors, and optimal treatment of MCC. METHODS: A multicenter, retrospective, consecutive study of patients with known primary MCC was completed. Overall survival and survival free of locoregional recurrence were calculated and statistical analysis of characteristics and outcomes was performed. RESULTS: Among the 240 patients, the mean age at diagnosis was 70.1 years, 168 (70.0%) were male, and the majority was Caucasian. The most common location was head and neck (111, 46.3%). Immunosuppressed patients had significantly worse survival, with an overall 3-year survival of 43.4% compared with 68.1% in immunocompetent patients. In our study, patients with stage II disease had improved overall survival versus those with stage I disease, in a statistically significant manner. Patients with stage III disease had significantly worse survival compared with stage I and with stage II. Primary tumor size did not predict nodal involvement. CONCLUSION: The data presented represent one of the largest series of primary MCC in the literature and confirm that MCC of all sizes has metastatic potential, supporting sentinel lymph node biopsy for all primary MCC. Because of the unpredictable natural history of MCC, we recommend individualization of care based on the details of each patient's tumor and clinical presentation.

The predictive value of imaging studies in evaluating regional lymph node involvement in Merkel cell carcinoma.

BACKGROUND: Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine malignancy with high potential for nodal or distant metastatic spread. Little information exists on sensitivity and specificity of various imaging techniques when compared with the gold standard of histopathologic evaluation of the lymph node basin. OBJECTIVE: We sought to further understand the value of various imaging modalities in the staging and initial workup of patients with MCC. METHODS: Of 240 patients with primary MCC evaluated between 1981 and 2008, 99 had diagnostic imaging at initial presentation with biopsy-proven cutaneous MCC and had histopathologic nodal evaluation within 4 weeks of the initial scan. We conducted a retrospective chart review of these identified patients. RESULTS: Computed tomography (n = 69) demonstrated a sensitivity of 47%, specificity of 97%, positive predictive value of 94%, and negative predictive value of 68% in detecting nodal basin involvement. Fluorine-18-fluorodeoxyglucose positron emission tomography scan (n = 33) demonstrated a sensitivity of 83%, specificity of 95%, positive predictive value of 91%, and negative predictive value of 91% in detecting nodal basin involvement. Magnetic resonance imaging (n = 10) demonstrated a sensitivity of 0%, specificity of 86%, positive predictive value of 0%, and negative predictive value of 67% in detecting nodal basin involvement. LIMITATIONS: This was a retrospective study with small sample size. CONCLUSION: Use of fluorine-18-fluorodeoxyglucose positron emission tomography in the evaluation of a regional lymph node basin in primary MCC is significantly more sensitive and equally specific when compared with traditional computed tomography. Both fluorine-18-fluorodeoxyglucose positron emission tomography and computed tomography are more sensitive than clinical examination alone.

Natural history of merkel cell carcinoma following locoregional recurrence.

BACKGROUND: Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine malignancy with an ill-defined natural history following locoregional recurrence. METHODS: This is a retrospective review of patients with MCC diagnosed at the Mayo Clinic from 1981 to 2008. For each outcome (subsequent locoregional recurrence, distant recurrence, and death) the survival-free of the outcome was estimated using the Kaplan-Meier method. Associations of patient and clinical characteristics with the outcomes were assessed by fitting Cox proportional hazards regression models. RESULTS: Among the 240 patients diagnosed with MCC, 70 (29%) patients were identified who developed locoregional recurrence as the first site of recurrence. The median time from diagnosis to locoregional recurrence was 6 months. The pattern of first locoregional failure in this group includes 25 (10.4%) local, 18 (7.5%) in-transit, and 27 (11.3%) nodal recurrences. Recurrences were most commonly treated by surgery and radiation. At 3 years after the initial recurrence, locoregional recurrence-free survival was 75% and the distant recurrence-free survival was 56%. Locoregional recurrence is a poor prognostic sign associated with a 3-year overall survival of 39%. Nodal status at time of original surgery and time to first recurrence were important predictors of distant recurrence (P < 0.006) and overall survival following locoregional recurrence (P < 0.001). CONCLUSIONS: Locoregional recurrence is a substantial problem in patients with MCC and is a poor prognostic sign. In those patients who experience a locoregional recurrence, aggressive efforts to regain locoregional control appear warranted and may result in long-term survival.