Abstract

     We report a case of a 74-year-old Caucasian male with a new 0.6 centimeter eroded pink papule at the left lateral cheek for two months that bled with manipulation. Tangential shave biopsy and histopathologic analysis of the patient’s new lesion demonstrated a lobular squamoproliferative growth with clear cell change, a thickened basement membrane, pleomorphic keratinocytes, and scattered mitotic figures. CD34 and p53 stains were positive in tumor cells while calretinin was negative.  The clinical and histopathologic findings confirmed a diagnosis of trichilemmal carcinoma. The patient underwent Mohs micrographic surgery with negative margins and subsequent intermediate linear closure.    

     Trichilemmal carcinoma is a rare, low-grade, malignant neoplasm originating from the outer root sheath of a hair follicle that is associated with sun exposed areas of elderly patients. The lesion is characterized by cells with clear glycogen rich cytoplasm, atypical nuclei, and pleomorphism as compared to trichilemmomas. Trichilemmal carcinomas have demonstrated positivity with PAS, CEA, EMA, CD34, and p53. The histopathologic differential diagnosis can include various adnexal neoplasms or clear cell tumors of the skin. Surgical treatment with either wide local excision or Mohs micrographic surgery is preferred, and recurrence or metastasis is rare. Dermatopathologists should be aware of the histopathologic findings of trichilemmal carcinoma to facilitate early diagnosis and treatment of this condition.