NEW YORK Subungual melanomas are often difficult to diagnose and thus present in an advanced clinical stage with poor prognosis, Dr. Richard Scolyer said at the Fourth International Melanoma Congress.
A review of the Sydney Melanoma Unit's experience between 1951 and 2004 showed that 124 patients presented with subungual melanoma (64 men and 60 women). The median patient age was 59 years, and the most common site was the great toe (24%). Most melanomas were locally advanced, with median Breslow thickness of 3.2 mm. Sentinel lymph node biopsy was positive in 24% (7 of 29 patients).
Follow-up data were available for 9 of 11 patients with in situ melanoma. American Joint Committee on Cancer disease stage at diagnosis, which was known in 121 patients, was the most important survival factor. Eleven patients (9%) were stage 0 (melanoma in situ), 16 (13%) were stage I, 50 (40%) were stage II, 39 (31%) were stage III, and 5 (4%) were stage IV.
The most common presentation in this group of patients was a pigmented subungual lesion or a raised or polypoid nodule, but "in more than one-third of patients (35%), there was no visible pigmentation in the affected area," said Dr. Scolyer of the University of Sydney.
Biopsies can be challenging to pathologists, in part because the features of melanoma in situ and the radial growth phase of melanoma are subtle. The most common early sign is longitudinal melanonychia. Particular red flags in these pigmented bands are increasing width, irregular width, and irregular spacing under dermoscopy, as well as extensions onto the proximal lateral nail fold (Hutchinson's sign). Subungual hematoma is important in the differential diagnosis, he said.
Unlike other melanomas, subungual melanoma is not associated with exposure to UV light, given that the nail plate is a UV barrier. Thus, incidence is similar among different ethnic backgrounds and skin tones. However, because melanomas in general are rare in people with darker skin, subungual melanomas make up a greater portion of melanomas among such persons, Dr. Scolyer noted.