Subungual Squamous Cell Carcinoma Treated by Topical Photodynamic Therapy

If you’ve ever brushed off a nail problem—like discoloration, pain, or separation from the bed—thinking it’s just a fungus or minor injury, you’re not alone. But for some people, those “small” changes can signal a rare, aggressive cancer: subungual squamous cell carcinoma (SCC), which grows under the nail. Now, a team of dermatologists from China has shared a case where a non-surgical treatment called topical photodynamic therapy (PDT) successfully treated this hard-to-manage cancer—and it could offer hope for patients who can’t or won’t have surgery.

The case, published in the Chinese Medical Journal in 2020 by Qian An, Song Zheng, Li Zhang, Xing-Hua Gao, and Jiu-Hong Li from the Department of Dermatology at The First Hospital of China Medical University (Shenyang, Liaoning), details how PDT helped a 66-year-old farmer with subungual SCC avoid surgery and regain a healthy nail.

What Is Subungual SCC?

Subungual SCC is the most common malignant tumor of the nail unit—but it’s still rare. Its symptoms (like nail thickening, discoloration, or pus) are often confused with fungal infections or chronic paronychia (nail bed inflammation), leading to misdiagnosis and delayed treatment, according to a 2015 BMJ Case Report. Risk factors include repeated trauma (like the patient’s farm work, where he handled corn by hand), radiation exposure, HPV infection, and rare genetic conditions like dyskeratosis congenita.

A Farmer’s Story: 18 Months of Nail Trouble

The patient had struggled with worsening nail problems for 18 months: his left thumb nail was separating from the bed (onycholysis), looking distorted, and oozing pus. A biopsy confirmed subungual SCC: tumor cells had broken through the skin’s basement membrane and invaded the deeper dermis, with abnormal, misshapen cells (pleomorphism) under the microscope. Tests for melanoma (using markers like HMB-45 and Melan A) were negative, so the diagnosis was clear.

Surgery—like Mohs micrographic surgery (a precise technique to remove cancer while preserving tissue) or even finger amputation—was recommended. But the patient refused. Since there was no evidence of bone involvement or spread, the team turned to topical PDT, a treatment already used for non-melanoma skin cancers like actinic keratosis and basal cell carcinoma (per a 2016 review in Dermatologic Surgery).

How PDT Worked for Him

PDT uses a light-activated drug to kill cancer cells. Here’s what the treatment involved:

Nail avulsion: Part of the nail plate was removed under local anesthesia (2% lidocaine) to expose the cancerous nail bed.
Drug application: A 20% aminolevulinic acid gel (a photosensitizing agent) was applied to the nail bed and covered with gauze for 3 hours to let it absorb.
Light activation: The area was irradiated with 635-nm red light (100 J/cm²) from a diode laser—this activated the drug, which produces reactive oxygen species to destroy cancer cells.

The patient had five sessions, one week apart.

The Result: A Healthy Nail, No Recurrence

Two weeks after treatment, the patient was healing well. Ten months later? His nail had regrown completely normally—no separation, no pus, and no clinical signs of cancer. The team continued to follow up, and as of the study’s publication, there was no recurrence.

PDT: Hope, But With Caution

Subungual SCC is tough to treat: surgery has high recurrence rates, and amputation can devastate quality of life. PDT is appealing because it’s quick, simple, and less invasive. But it’s not a “one-size-fits-all” solution. While some early SCC cases respond well, PDT can fail—and if it does, the cancer might spread. That’s why the team emphasized close long-term follow-up—critical for catching any recurrence early.

As the authors note, PDT isn’t routinely recommended for invasive SCC (like this patient’s case). But for those who can’t have surgery, it’s a promising option—especially since another 2019 case in the Australasian Journal of Dermatology found 14 years of remission in a patient with subungual Bowen disease (a pre-cancerous condition) treated with PDT.

What This Means for Patients

This case offers hope for people with subungual SCC who want to avoid surgery. But it’s important to remember: early diagnosis is key. If you notice persistent nail changes (like lasting discoloration, pain, or separation), see a dermatologist—don’t wait. And if surgery isn’t an option, ask about PDT—just be sure to discuss the risks and benefits with a specialist.

Original study: An Q, Zheng S, Zhang L, Gao XH, Li JH. Subungual squamous cell carcinoma treated by topical photodynamic therapy. Chinese Medical Journal. 2020;133(7):881–882. doi:10.1097/CM9.0000000000000723

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