Published on
Download the article PDF: Clinical Image Challenges October 2025
Differential Diagnosis
- Atypical fibroxanthoma
- Merkel cell carcinoma
- Pyogenic granuloma
- Keratoacanthoma
- Amelonatic melanoma
- Squamous cell carcinoma
- Microcystic adnexal carcinoma
- Nodular basal cell carcinoma
Diagnosis
This patient is diagnosed with Merkel cell carcinoma (MCC), also known as cutaneous neuroendocrine carcinoma. MMC is a rare aggressive skin malignancy that typically appears on the face, head or neck of adults between the age of 75-80 years. MMC most commonly arises in fair-skinned males and often appears on the head and face, upper extremities, and torso. Lower extremity presentation is more common for darker skinned individuals with erythema appearing more subtle. Key risk factors include older age, ultraviolet light exposure, immunosuppression, concurrent hematologic malignancy and infection with the Merkel cell polyomavirus (MCPyV). Even with aggressive treatment, reoccurrence probability is high with metastases common. There is a 5-year relative survival is approximately 60% in the United States.
What To Look For
- Presents as an asymptomatic, flesh-colored or bluish-red, firm, non-tender, shiny, solitary, rapidly growing nodule, usually between 0.5-5.0 cm in size. Ulceration and crusting are relatively infrequent.
- Neurologic symptoms such as ataxia, weakness, and confusion may be present.
Pearls for Urgent Care Management
- MCC is often misdiagnosed as a benign skin lesion, therefore a high clinical suspicion is required to diagnose it in its early stages.
- Remember AEIOU when considering history and exam findings: Asymptomatic/lack of tenderness, Expanding rapidly (doubling in <3 months), Immunosuppression, Older than 50 years, Ultraviolet exposed skin site.
- Prompt biopsy is indicated for definitive diagnosis; either narrow-margin punch biopsy in clinic or urgent referral to dermatology is appropriate.