Dermoscopic Features of Subungual Squamous Cell Carcinoma: A Study of 44 Cases.

BACKGROUND: Subungual squamous cell carcinoma (SSCC) is the most frequent tumor of the nail apparatus. Its diagnosis is often missed or delayed because the clinical presentation is atypical and can mimic other conditions. Accurate diagnosis can only be made by performing an appropriate surgical biopsy, but biopsy is painful and often leaves definitive dystrophic scars. The use of dermoscopy, a noninvasive technique, has been described to be useful for the preoperative evaluation of nail diseases. OBJECTIVES: To define the different clinical and dermoscopic presentations of SSCC and to compare them with onychomatricoma-associated clinical and dermoscopic features published in our previous study. METHODS: A retrospective review of 44 cases of SSCC seen in our institution over an 8-year period. Six observers scored 19 clinical criteria and 14 dermoscopic criteria as present or absent. Then, we compared those data to a previously published study about the preoperative diagnosis of onychomatricoma. RESULTS: Only 1 dermoscopic criterion was significantly associated with SSCC compared to onychomatricoma: localized hyperkeratosis (odds ratio, OR = 6.25, p = 0.012, 95% confidence interval CI = 1.50-26.01). In contrast, parallel edges (OR = 0.03, p < 0,001, 95% CI = 0.003-0.20) and sharp demarcation of the lesion (OR = 0.24, p = 0.004, 95% CI = 0.09-0.63) can statistically significantly be considered as in favor of onychomatricoma. By contrast, we believe that the presence of unparalleled lateral edges of the nail lesion or of fuzzy edges are more in favor of SSCC. CONCLUSIONS: Dermoscopy of the nail plate and of the nail free edge in SSCC provides useful information in order to better select cases to be submitted to biopsy.

Dermoscopic Features of Onychomatricoma: A Study of 34 Cases.

BACKGROUND: Onychomatricoma is a benign tumor of the nail matrix with a precise histopathological definition but many different clinical features and differential diagnoses. OBJECTIVES: The diagnosis of onychomatricoma is based on the pathological examination of a surgical specimen. The objective of this study was to define preoperative diagnostic criteria using noninvasive investigations: observation and dermoscopy. METHODS: A total of 34 cases of onychomatricoma were studied. In detail, 6 observers evaluated 12 clinical and 12 dermoscopical criteria as present or absent. RESULTS: For clinical criteria, the highest mean values were leuconychia (3.21), splinter hemorrhages (3.45), and thickening of the plate (3.0). Dermoscopical criteria were more often found present, such as longitudinal parallel white lines (4.33), parallel lesion edges (4.61), splinter hemorrhages (4.48), dark dots (3.96), free-edge nail pitting (4.5), and thickening of the free edge (5.27). CONCLUSION: Dermoscopical criteria for onychomatricoma are more frequently present and less subject to divergent interpretation. This offers new and original preoperative reliable diagnostic criteria and should be used in the evaluation of nail tumors.