Patients with Merkel cell carcinoma tumors ≤ 1.0 cm in diameter are unlikely to harbor regional lymph node metastasis

Purpose: Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine cutaneous malignancy. Current recommendations include offering regional lymph node evaluation by either sentinel lymph node biopsy (SLNB) or complete lymph node dissection (CLND) to all patients with MCC; however, we hypothesized a cohort of low-risk patients may exist for whom regional nodal metastasis would be unlikely. Methods: A retrospective review of the Department of Veterans Affairs national health care database was performed. Patients undergoing resection of primary MCC were identified; and demographic, medical, and social history; tumor characteristics; nodal status; and recurrence events were recorded. Results: Between 1995 and 2006, 346 patients were diagnosed with MCC. Of these, 213 underwent resection of the primary lesion and evaluation of the draining lymph node basin. Fifty-four patients (25%) had tumors ≤ 1.0 cm in diameter. Average tumor diameter was 0.7 cm, and 63% were located on the head or neck. Only two patients (4%) with tumors ≤ 1.0 cm had regional lymph node metastasis, compared with 51 (24%) of 213 patients with tumors more than 1.0 cm (P ≤ .0001). Both patients had clinically evident nodal disease at presentation and underwent CLND. Both have remained recurrence-free for 40 months. Thirteen (25%) of 51 patients with nodal metastasis and tumors more than 1 cm had occult nodal metastasis. Conclusion: In this series, patients with MCC ≤ 1.0 cm were unlikely to have regional lymph node metastasis, suggesting that regional nodal evaluation may reasonably be avoided in these patients. However, these data support SLNB for MCC more than 1 cm in diameter.