Emphasizing that the varying clinical presentation of squamous cell carcinoma can lead to late diagnosis and treatment, this author offers pertinent insights on subungual squamous cell carcinoma of the nail bed.
Subungual squamous cell carcinoma is a rare malignancy that can affect both the toes and fingers. Researchers note that numerous factors can contribute to the development of subungual squamous cell carcinoma, including human papilloma virus (HPV), chronic trauma, chronic inflammation and radiation exposure.1 This disorder’s variable clinical presentation, which can mimic many benign pathologies, often leads to delayed diagnosis and treatment.
I present a case of subungual squamous cell carcinoma diagnosed with nail bed biopsy and treated with surgical excision of the nail bed and matrix.
Keys To The Patient Presentation
A 62-year-old woman presented to our clinic with chief complaints of ankle pain and great toe joint pain and deformity. Incidentally, the patient mentioned discoloration of her left great toenail of one-year duration that she had unsuccessfully tried to remove by filing off. Other than sun exposure, the patient had no other risk factors for squamous cell carcinoma such as immunosuppression, trauma or prior HPV infection.
The physical exam revealed a linear pigmented streak below her left hallux nail plate (see above left photo). Radiographs showed no underlying osseous changes (see below right photo). I recommended initial conservative care for her musculoskeletal conditions but given the atypical appearance of her nail plate lesion, I did recommend urgent nail plate avulsion and biopsy.
The patient initially declined any intervention but later was amenable to nail plate avulsion and biopsy when receiving surgical intervention for her bunion deformity and chronic ankle pain. Intraoperatively, I avulsed the left hallux nail plate and there was a dark hyperpigmented band along the entire hallux nail bed.
I obtained a 3 mm punch biopsy from the area of the nail matrix. Pathologic analysis of this specimen revealed an irregular acanthotic epidermis with overlying parakeratosis. The epidermis exhibited full-thickness dysplasia with keratinocytes demonstrating large pleomorphic nuclei and occasional mitosis consistent with squamous cell carcinoma in situ. The carcinoma extended to the biopsy margins.
After discussion with the patient’s dermatologist, I recommended complete surgical excision of the nail matrix and nail bed. After excising the nail matrix and bed, I performed a local rotational flap closure. Pathologic analysis showed residual squamous cell carcinoma in situ with negative resection margins and no evidence of invasive carcinoma. At approximately six months postoperative, the patient has shown no evidence of recurrent disease.
What You Should Know About Squamous Cell Carcinoma In The Nail Bed
Malignancy of the nail apparatus is rare. Subungual squamous cell carcinoma represents the most common of these malignancies. This tumor occurs most commonly in men between 50 and 70 years of age, and affects fingers more commonly than toes.1 Several factors reportedly predispose individuals to subungual squamous cell carcinoma, including HPV, chronic trauma, chronic inflammation, chronic infection, ionizing radiation, solar radiation, tar, arsenic or other mineral exposure and immunosuppression.2-5 Researchers have reported HPV to be an etiological factor in the development of subungual squamous cell carcinoma of the fingers but the role of HPV in the development of squamous cell carcinoma of the feet is unclear.5
The most common clinical presentation of subungual squamous cell carcinoma is a wart-like appearance of the nail bed and periungual skin with dystrophic nail plate changes.3,6,7 However, clinical presentation can also include chronic pain, swelling, onycholysis, nail plate discoloration, nodularity and ulceration.3,6,7 The clinical features of subungual squamous cell carcinoma are variable and often mimic benign conditions, frequently leading to long delays in diagnosis. The differential diagnosis for subungual squamous cell carcinoma can include verruca vulgaris, onychomycosis, pyogenic granuloma, traumatic onychodystrophy, paronychia, psoriasis and melanoma.2
Nail plate avulsion with nail bed biopsy is the gold standard for the diagnosis of subungual squamous cell carcinoma.4,8 Unlike the hand, the role of HPV in the development of squamous cell carcinoma of the feet has not been well established.5 While it is not a standard diagnostic practice, one may consider HPV typing in higher-risk individuals given that HPV-associated squamous cell carcinoma can be associated with more invasive disease. Radiographs are recommended in the evaluation of subungual squamous cell carcinoma as bone involvement reportedly occurs in up to 20 percent of cases.2 While researchers have reported inguinal lymph node involvement, this occurrence is rare and sentinel node biopsy is not typically indicated in the management of subungual squamous cell carcinoma.2,6
Owing to the rarity of this malignancy, subungual squamous cell carcinoma does not have a standardized treatment protocol. Surgical management depends on the size and invasiveness of the tumor. Authors typically recommended surgical excision with a margin of 5 mm.2 One can often manage squamous cell carcinoma in situ with excision of the nail apparatus with local flap or skin graft coverage whereas invasive lesions often require digital amputation.1,9,10
Frequently, one diagnoses squamous cell carcinoma after treatment failure for more benign conditions. Late diagnosis often leads to more invasive disease and worse disease prognosis. This case study highlights the importance of performing early biopsy of nail bed abnormalities for pathological confirmation of disease.
Dr. Hoffman is an Attending Physician in the Department of Orthopedics at Denver Health Medical Center in Denver. She is an Assistant Professor in the Department of Orthopedics at the University of Colorado School of Medicine.
1. Kelly KJ, Kalani AD, Storrs S, et al. Subungual squamous cell carcinoma of the toe: working toward a standardized therapeutic approach. J Surg Educ. 2008;65(4):297-301.
2. Padilha CB, Balassiano LK, Pinto JC, Souza FC, Kac BK, Treu CM. Subungual squamous cell carcinoma. An Bras Dermatol. 2016;91(6):817-819.
3. Meesiri S. Subungual squamous cell carcinoma masquerading as chronic common infection. J Med Assoc Thai. 2010;93(2):248-251.
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7. Ruiz Santiago H, Morales-Burgos A. Cryosurgery as adjuvant to Mohs micrographic surgery in the management of subungual squamous cell carcinoma. Dermatol Surg. 2011;37(2):256-258.
8. Kranc CLVE, D. What is causing these nail changes? Dermatologist. 2013;21(2).
9. Dalle S, Depape L, Phan A, Balme B, Ronger-Savle S, Thomas L. Squamous cell carcinoma of the nail apparatus: clinicopathological study of 35 cases. Br J Dermatol. 2007;156(5):871-874.
10. Alghamdi I, Robert N, Revol M. Fingertips squamous cell carcinoma: Treatment outcomes with surgical excision and full thickness skin graft. Ann Chir Plast Esthet. 2016;61(1):39-43.