Merkel cell carcinoma under 50: often immunosuppressed and often node-positive at diagnosis

Design

Single-centre retrospective case series

Population

13 patients aged 18-50 with Merkel cell carcinoma, 2009-2025

Primary outcome

Clinicopathological features and survival

Effect

Nodal metastases at presentation 60%; 5-year overall survival 59.3%

A tertiary centre reviewed all patients aged 18 to 50 diagnosed with Merkel cell carcinoma from 2009 to 2025 (American Journal of Surgical Pathology, 9 October 2026). There were 13, median age 40. Of 11 with data, 36.4% had pre-existing immunosuppression. Tumours were deep (median Breslow depth 10.5 mm) and highly mitotic (median 46/mm²). Merkel cell polyomavirus was detected in 5 of 8 assessable cases.

Nodal metastases were present at presentation in 60%, distant metastases developed in 54.5%, and estimated five-year overall survival was 59.3%. The series is small, but the message for the reporting pathologist is that a small-round-blue-cell tumour of skin in a younger adult should still prompt Merkel cell markers.

• Include Merkel cell carcinoma in the differential for a small round cell skin tumour even under 50.
• Ask about immunosuppression when the diagnosis is made in a younger patient.
• Report depth and mitotic rate; tumours in this series were deep and highly proliferative.
• Flag the need for nodal staging; 60% had nodal disease at presentation.

Why it matters

Age is often used as a shortcut in skin differentials, and here it would mislead.

Don't overread it

With 13 patients from one centre, the percentages are unstable.

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