Abstract:

Pilomatrix carcinoma is a rare, locally aggressive neoplasm with approximately 135 cases reported worldwide, and is associated with a significant risk of recurrence and metastasis. It remains a purely histological diagnosis, as available molecular and immunohistochemical methods do not distinguish between benign and malignant variants of pilomatrix origin. A 49-year-old Fitzpatrick skin type III female presented with a two-month history of a rapidly enlarging nodule of the right cheek that progressed despite multiple courses of oral antibiotics and an attempted incision and drainage. She presented with a well-circumscribed 12x10mm firm, nontender, violaceous nodule of the right cheek with increased vascularity, ulceration, and several discrete aggregates of light brown pigment. Histopathologic examination of the excisional biopsy specimen revealed an atypical basaloid proliferation forming infiltrative nodules invading into the dermis and subcutis. Anucleate matrical corneocytes (shadow cells) were present. The basaloid proliferation exhibited cytologic atypia, increased mitotic activity, and focal necrosis, consistent with a diagnosis of pilomatrix carcinoma. Clinical lymphadenopathy was absent and a PET/CT did not demonstrate metastasis. She underwent Mohs micrographic surgery (MMS), where intradepartmental collaboration with a dermatopathologist aided in confirming the tumor-free plane at the fifth stage. She underwent reconstruction of the lateral right cheek defect and is currently receiving adjuvant radiation therapy in an effort to reduce the risk of tumor recurrence. Treatment of facial pilomatrix carcinoma with MMS has rarely been reported in the literature. This case underscores the distinguishing histologic features of pilomatrix carcinoma that are critical to confirming the diagnosis and highlights the utility of MMS for treatment of this rare neoplasm.

Financial Disclosure:
No current or relevant financial relationships exist.

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Colin Nolan, MD

Biography