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Case Reports

Abstract

Pilomatrix carcinoma, also known as calcified epithelial carcinoma of Malherbe, is a rare, malignant neoplasm that is derived from follicular matrix cells. These neoplasms are considered locally invasive with cases of metastasis, most commonly to lymph nodes, bone, or lung. There are no current guidelines for treatment of pilomatrix carcinoma, although most case reports recommend wide local excision with or without chemotherapy or radiation. This report describes a case of pilomatrix carcinoma to the left ear without known history of a previous mass to the area. A 79-year-old male with a pertinent past medical history of non-melanoma skin cancer presented with a tender, firm, erythematous nodule to his left ear, present months. The initial clinical differential diagnosis included gout, a calcified nodule, or a non-melanoma skin cancer. Histopathology revealed large nests and infiltrative strands of basaloid cells with prominent shadow cell formation. The cells were pleomorphic with many atypical mitoses. Immunohistochemistry revealed the tumoral cells to stain p40 (+), BCL2 (-), Beta-catenin (+, nuclear), and S100 (-). A diagnosis of pilomatrix carcinoma was made, and the patient underwent Mohs micrographic surgery, which cleared the tumor in one stage. This case brings awareness to a rare neoplasm without clear treatment guidelines, often misdiagnosed clinically.