A rapidly growing scalp nodule

Merkel cell carcinoma — vertex of scalp

Learning points

• The AEIOU mnemonic prompts biopsy of any rapidly growing cutaneous nodule in an older, sun-damaged patient.
• CK20 paranuclear dot pattern + TTF-1 negativity is the diagnostic IHC signature for Merkel cell carcinoma.
• Locoregional management: wide local excision + sentinel lymph node biopsy + adjuvant radiotherapy to primary site (and nodal basin if SLN positive).
• Metastatic Merkel cell carcinoma is first-line treated with avelumab (NICE TA691). Pembrolizumab has KEYNOTE-017 evidence in advanced MCC, but no NICE pembrolizumab MCC TA was identified on live checking; confirm access route before use.
• MDT-mandatory disease — early input from clinical and medical oncology.