Merkel cell carcinoma of unknown primary: Clinical presentation and outcomes

Abstract

Background Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous malignancy that usually occurs in the head/neck or extremities. However, there are reports of MCC developing in the lymph nodes or parotid gland without evidence of a primary cutaneous lesion. Methods We reviewed 415 patients with biopsy‐proven MCC. Patients with MCC of unknown primary (n = 37, 9%, MCCUP) made up the study cohort. The primary endpoints of the study were rate of recurrence, disease‐free survival, and overall survival. Results Patients with MCCUP presented with tumors in lymph nodes (n = 34) or parotid gland (n = 3). Nodal disease was most commonly detected in the inguinal/external iliac (n = 15) or axillary (n = 14) regions. The mean age at diagnosis was 70 years and 24% were female. Patients presented with distant metastases in 24.3% of cases. Patients with stage IIIA disease treated with regional lymph node dissection (RLND) had a lower risk of disease recurrence (hazard ratio 0.26, p = 0.046). Recurrence‐free survival was 59.3% at 5 years. Disease‐specific survival was 63.3% at 5 years. Conclusion Patients with MCCUP have a high risk of recurrence and mortality. The optimal treatment for MCCUP has yet to be elucidated, although therapeutic RLND appears beneficial for these patients.

Multidisciplinary Treatment of Merkel Cell Carcinoma of the Extremities: Outcomes and Factors Associated with Poor Survival in Nodal Disease

“…The Eighth Edition of the AJCC staging system for Merkel cell carcinoma stratifies stage III disease based on microscopic nodal disease (stage IIIa) versus macroscopic nodal disease that is seen on examination or imaging (stage IIIb). We have previously reported on an additional subset of stage IIIa disease involving patients with macroscopic nodal disease and no identifiable primary lesion [11]; however, the clinical significance of stage IIIa versus stage IIIb in the presence of a cutaneous primary lesion has not been well described.…”

Color Analysis of Merkel Cell Carcinoma: A Comparative Study with Cherry Angiomas, Hemangiomas, Basal Cell Carcinomas, and Squamous Cell Carcinomas

“…MCC presents a diagnostic challenge due to its nonspecific clinical characteristics (Figure 2. It is frequently misdiagnosed as either a harmless skin lesion like a cyst, lipoma, cherry angioma, hemangioma, or other types of non-melanoma skin cancer, such as basal cell carcinoma or squamous cell carcinoma [1,11,12]. A study involving 195 patients diagnosed with MCC highlighted the difficulty in assessing the specificity of the clinical features of MCC [13].…”

A review on the oncogenesis of Merkel cell carcinoma: Several subsets arise from different stages of differentiation of stem cell

“…Merkel cell carcinoma (MCC), a rare primary cutaneous neuroendocrine neoplasm, is extremely aggressive and has a higher mortality rate than melanoma. [ 1 , 2 ] In the United States, the annual incidence of MCC was 0.7/100,000 persons in 2013, and there has been an exponential global increase over the past 30 years. [ 3 , 4 ] Risk factors for developing MCC include chronic ultraviolet (UV) exposure, immunosuppression, skin fires, and older age.…”