Hypertrophic lichen planus mimicking squamous cell carcinoma

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 reclassified 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, flat-topped 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

Hypertrophic lichen planus mimicking squamous cell carcinoma: The importance of clinicopathologic correlation

“…This case underscores the importance of recognizing HLP as a mimicker of SCC to avoid unnecessary interventions and ensure timely initiation of appropriate treatment. At least 4 patients with HLP mistaken as SCC have been reported in the literature, highlighting the challenge of identifying the correct diagnosis 2, 3…”

“…Typical features of LP, including hypergranulosis and basal cell vacuolar degeneration, may not be present 2 . Like other chronic inflammatory conditions associated with rubbing and irritation, HLP may be associated with features of pseudoepitheliomatous hyperplasia (PEH), which can be difficult to distinguish from SCC 2, 6. PEH is characterized by hyperplasia of the epidermis and adnexal epithelium, gross irregular acanthosis, and horn cyst formation 2, 3, 6.…”

“…Like other chronic inflammatory conditions associated with rubbing and irritation, HLP may be associated with features of pseudoepitheliomatous hyperplasia (PEH), which can be difficult to distinguish from SCC 2, 6. PEH is characterized by hyperplasia of the epidermis and adnexal epithelium, gross irregular acanthosis, and horn cyst formation 2, 3, 6. However, unlike SCC, PEH does not infiltrate into the reticular dermis or invade blood vessels, nerves, or lymphatics 2, 3…”

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

“…However, histologic clues that point to PEH include a lichenoid infiltrate at the tips of the rete ridges along with dyskeratosis, pigment incontinence, lack of cytologic atypia, and proliferation from follicular infundibula 4,5 . Furthermore, clinical clues such as response to steroids and multiplicity and acuity of lesions may be more useful than histopathology to indicate PEH rather than SCC 1,3,4 .…”

“…Similarly, multiple studies have commented on the difficulty of differentiating SCC from PEH arising from hypertrophic LP histologically, and a multitude of prior cases have been reported in which the preliminary diagnosis of SCC was reversed to hypertrophic LP following supportive clinical evidence 1,3 . In the majority of these cases the lesions showed significant improvement with near-resolution by 6 months following treatment with topical steroids 1 .…”