MANCHESTER, ENGLAND — Squamous cell carcinoma of the nail unit is often misdiagnosed and its painful course protracted because clinical features can resemble more mundane conditions such as paronychia, Dr. Mohamed Alrawi said at the annual meeting of the British Association of Dermatologists.
A retrospective study of 20 patients seen between 1997 and 2005 has identified three patterns of presentation in this rare condition, and wider recognition of these patterns could help expedite diagnosis, Dr. Alrawi said. The clinical patterns were:
▸ Type 1, in 10 (50%) patients, was a frank nodule or tumor with or without nail loss.
▸ Type 2, seen in six (30%), was a mild to moderate warty periungual lesion with nail splitting and skin fissures.
▸ Type 3, found in four (20%), was a recurrent discharge from beneath the nail with putative onychomycosis.
In all patients, less than 50% of the surface area of the distal phalanx was affected, said Dr. Alrawi of Bristol Dermatology Centre, Bristol (England) Royal Infirmary.
One patient had bone involvement. Histologic evaluation showed invasive disease in 15 patients, 5 with in situ squamous cell carcinoma. The thumb was the most commonly affected digit, involved in seven of the patients. The index finger was affected in four patients, the middle finger in three, and the ring and little fingers in one each.
A total of 14 patients reported pain as the primary symptom, and only 2 were asymptomatic, he said. In seven patients, the carcinoma was associated with human papillomavirus, with six involving type 16.