A case of hypertrophic lichen ruber planus of the leg complicated by a squamous cell carcinoma

A case of hypertrophic lichen ruber planus of the leg complicated by a squamous cell carcinoma In November 2000, a 58-year-old man suffering from longstanding (20 years) and histologically documented hypertrophic lichen planus (LP) of the legs (Fig. 1), with no other additional cutaneous or mucosal involvement, was referred for the evaluation of the development of an exophytic neoformation within the context of an LP skin lesion. After a physical examination, a 3 × 2-cm, well-outlined, easily bleeding verrucous nodule was evident over a plaque of hypertrophic LP located in the pretibial area of the right leg (Fig. 2). No history of arsenicals, ionizing radiation treatment, topical application of coal tar, or systemic administration of immunosuppressive drugs was found; the patient had stopped topical application of corticosteroids 12 months before the tumor appeared. Wide surgical excision of the cutaneous lesion was performed. Within the context of the LP plaque, a cutaneous neoplastic proliferation of large, polygonal, keratinizing, welldifferentiated, abnormally oriented squamous cells, with deep dermis invasion, was evident. The tumor presented rare atypical mitoses and areas of maturation forming parakeratotic horny pearls. On immunohistochemical evaluation, proliferating markers showed a variable grade of staining: monoclonal antibodies against monoclonal mouse antiproliferating cell nuclear antigen (PCNA) stained more than 70% of deeper invading neoplastic cells. High proliferating malignant cells of the nodular component reacted strongly with monoclonal mouse anti-human ki67 antigen (Mib-1), whose expression dramatically decreased between the tumor and LP lesion. Rare atypical mitoses, located in the deep, more aggressive part of the neoplasm, were labeled by p53 with strong expression. A diagnosis of well-differentiated squamous cell carcinoma (SCC) associated with hypertrophic LP was made.