Hypertrophic Lichen Planus versus Well-Differentiated Squamous Cell Carcinoma: A Histological Challenge 

Abstract

A 74-year-old woman presented with a 3 month history of an itchy rash on the dorsal forearms and left anterior shin. Physical exam revealed violaceous scaly papules and plaques along the dorsal forearms, as well as a hyperpigmented verrucous plaque with nodules along the left anterior shin (figure 1). Initial biopsy of the left anterior shin revealed well-differentiated squamous cell carcinoma (SCC, figure 2); however, due to a clinical appearance consistent with hypertrophic lichen planus (LP), three more biopsies were taken. Two of these were read as hypertrophic LP, while the third was analyzed as a non-specific squamous proliferation. The initial biopsy was subsequently re-classified as pseudoepitheliomatous hyperplasia (PEH), and the patient was diagnosed with hypertrophic LP and underwent improvement with clobetasol and kenalog treatment.A 55-year-old female on hemodialysis for chronic kidney disease presented with a 7 month history of an itchy rash on the extremities and back. Physical exam revealed many excoriated papules and nodules along with some lichenified, flattopped papules throughout all of these ABSTRACT Differentiating hypertrophic lichen planus (LP) from well-differentiated squamous cell carcinoma (SCC) is a histological challenge given the numerous histopathologic similarities between SCC and pseudoepitheliomatous hyperplasia (PEH) arising in the setting of hypertrophic LP. Multiple reports have shown that SCC can arise from hypertrophic LP not infrequently, but that the LP-to-SCC sequence is poorly understood, and many cases defy diagnosis due to histologic similarities. However, there are several clinical clues and histopathologic details that have shown to have some value when trying to ascertain the correct diagnosis. To the contrary, immunohistochemical tests have shown little promise in differentiating hypertrophic LP from SCC. Although multiplex PCR has shown some potential in differentiating PEH from SCC, this has only been in the setting of patients diagnosed with prurigo and lichen simplex chronicus, but not necessarily in the case hypertrophic LP. CASE DESCRIPTIONS