Lichenoid keratosis: non-invasive imaging in the setting of diagnostic uncertainty

A 60-year-old male presented with a solitary, asymptomatic, erythematous annular plaque on the medial portion of his right distal leg. Clinically, the lesion had central atrophy with peripheral hyperpigmentation, elevation and scaling (Figure 1). The differential diagnosis at clinical examination included: granuloma annulare, angular lichen planus, hypertrophic tinea corporis, and pigmented Bowen’s disease. Dermatoscopic imaging with polarized light demonstrates a non-chaotic lesion. There were two basic patterns; a central structureless and peripheral brown, thick, curved lines. Scattered red dots were found in the periphery, these correspond to pin point or coiled blood vessels. (Figure 2). Clues for a dermatofibroma include the central hypopigmentation and structureless pattern. There is a single clue for Bowen’s disease; a structureless pattern. There are three clues suggestive of a lichenoid keratosis; brown thick curved lines; central structureless, and peripheral red dots. The differential diagnosis of a lichenoid keratosis supersedes that of a seborrheic keratosis because the peripheral red dots and structureless pattern indicate that there is an inflammatory process suggestive of central regression. Although lichenoid keratosis is a likely diagnosis, dermatoscopic examination is diagnostically inconclusive. Further visualization is needed to rule out pigmented Bowen’s disease. Lichenoid keratosis: non-invasive imaging in the setting of diagnostic uncertainty