Nonhealing ulcer on the fingertip

What is Your Diagnosis?

Discussion

Stain for acid-fast bacilli and culture for mycobacteria and fungus from the pus were negative. Histopathology showed cohesive groups of keratinocytes having pleomorphic large vesicular nuclei with prominent nucleoli, and loss of polarity infiltrating into the underlying dermis. A few dyskeratotic keratinocytes and mitotic figures were also seen [Figure 2a and b]. Polymerase chain reaction was positive for human papillomavirus-16, 18 and 33 in the skin biopsy specimen. Radiograph showed erosion at the tip of the distal phalanx of the fifth digit [Figure 3]. The left fifth finger was disarticulated at the distal interphalangeal joint under ring block by the surgical oncology team, and adequate margins were confirmed on histopathology. The patient had no recurrence during the 1-year follow up period.

Close

Figure 3:

X-ray of the left hand showing mild erosion of left 5^th distal phalanx

Export to PPT

Subungual squamous cell carcinoma is a rare entity. Typically, it presents as a warty growth affecting the nail bed and periungual areas with associated nail dystrophy. However, clinical presentations are varied and it often gets mistaken for benign entities such as verruca vulgaris, onychomycoses, chronic paronychia, cellulitis or other chronic infections.¹ Because of protean manifestations, secondary infections, lack of visibility of the tumor beneath the nail plate coupled with a lack of awareness among clinicians, correct diagnosis of this entity is often delayed, by an average of 4–40 years.^2-4 In our case also, the diagnosis of squamous cell carcinoma was not suspected clinically because of the non-characteristic morphology of the ulcer and its atypical location. Further, the history of trauma during farming work and partial improvement with antibiotics proved to be a red herring leading us to suspect an infectious etiology for the fingertip ulcer. Farmers are at risk of acquiring deep fungal or non-tubercular mycobacterial infections through a wood splinter injury or soil contamination of the wound. Sporotrichosis and atypical mycobacterial infections can present as non-healing ulcers on fingertips.⁵

Despite the initial delay in diagnosis, the prognosis for subungual squamous cell carcinoma is largely favorable. It is considered a low-grade malignancy and is less aggressive than squamous cell carcinoma at other anatomical locations. Underlying bone involvement has been reported in 16–66% of patients, and nodal involvement in about 2% of patients. Tumor resection is usually curative with a low risk of recurrence or metastases.^1,2,6 Though the risk factors are poorly understood, exposure to known carcinogens such as arsenic, grease oil, radiation, repetitive trauma and friction, immunosuppressive states such as in a transplant recipient and human papillomavirus infection have been implicated. ¹ Human papillomavirus-16 has been identified most commonly among the human papillomavirus-associated ungual and periungual squamous cell carcinomas.⁷ Infection with this and other high-risk types seems to have predisposed our patient to the development of squamous cell carcinoma. However, he did not have a history or presence of anogenital warts, suggesting that he may have been infected through a nongenital contact with someone having high-risk papillomavirus infection. The role of repetitive trauma as a contributing factor cannot be ruled out, given our patient’s occupation. To conclude, the diagnosis of subungual squamous cell carcinoma can be challenging. Dermatologists should be aware of this atypical location and should keep a high index of suspicion for squamous cell carcinoma for chronic recurrent or persistent nail unit lesions not responding to conventional treatment.