BackgroundAlthough squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) can be easily diagnosed clinically, proper diagnosis is sometimes difficult when based on clinical information alone.ObjectiveTo know what causes clinical misdiagnosis between SCC and BCC, and evaluate whether dermoscopy can improve diagnostic accuracy.MethodsClinical and dermoscopic photographs of inversely diagnosed cases (histologically confirmed BCC with a clinical impression of SCC or vice versa) were randomly presented to six dermatologists and the reasons for each correct or incorrect diagnosis were analyzed.ResultsAmong 154 cases (SCCs or BCCs), 13 cases were inversely diagnosed; 9 SCCs were clinically misdiagnosed as BCC and 4 BCCs were clinically misdiagnosed as SCC. Clinically, scales, pigmentation and rolled border were meaningful factors to discern two carcinomas. Scales without both pigmentation and rolled border was favored for SCC, but BCC favored vice versa. Ulceration, telangiectasia and translucency contributed as confusing factors for proper diagnosis. Dermoscopy improved overall diagnostic accuracy to odds ratio 2.86.ConclusionSCC has a higher tendency to be clinically misdiagnosed as BCC than vice versa. Pigmentation and rolled border are factors causing misdiagnosis of SCC as BCC and BCC may be misdiagnosed as SCC in the presence of scaling. Dermoscopy seems to improve the clinical diagnostic accuracy but has limitations for some ambiguous lesions.

Tinea incognito is a dermatophytic infection induced by immunosuppressive agents that lacks the classic features of a typical fungal infection. Although the treatment of tinea incognito is simple and relatively easy, its clinical manifestation varies and can masquerade as various skin disorders, causing misdiagnosis and thus preventing prompt and appropriate treatment. Here, we report an interesting case of tinea incognito occurring after topical steroid administration in an immunosuppressed patient with dermatitis artefacta. A 40-year-old female patient who had been taking systemic glucocorticoid for 4 years for chronic inflammatory demyelinating polyneuropathy presented with itching multiple erythematous erosive lesions on the face and upper chest for 2 months. Initial biopsy produced nonspecific findings. The skin lesion was aggravated and became polycyclic and erythematous; after azathioprine was added, her chronic inflammatory demyelinating polyneuropathy became aggravated. A second biopsy confirmed hyphae in the cornified layer. Complete remission was achieved after admonishing oral terbinafine and topical amorolfine.

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