Track: Case Reports

Abstract:

A 45-year-old, otherwise healthy female presented to the emergency department for evaluation of an enlarging mass behind the left ear for 3 years, which had become increasingly friable and tender over the past 6 months. Physical examination revealed a 7.5 x 5 x 2.5 cm fungating tumor with bleeding erosions and fibrinous exudate located on the post-auricular scalp. The differential diagnosis favored a malignant neoplasm, such as a squamous cell carcinoma (SCC) or melanoma. A shave biopsy was performed which showed a proliferation of atypical keratinocytes with hyperchromatic and pleomorphic nuclei in the epidermis extending through the papillary dermis and into the reticular dermis, with an inflammatory dermal infiltrate as well as overlying hyperkeratosis and parakeratosis. These findings were consistent with a well-differentiated SCC, though it was noted the lesion may have arisen from a proliferating trichilemmal tumor (pilar cyst). Proliferating trichilemmal tumors (PTT) are rare neoplasms arising from the outer root sheath of hair follicles. Malignant proliferating trichilemmal tumors (MPTT) are even less common, with fewer than 100 cases reported. Both benign and malignant PTT most commonly present on the scalp of elderly females. Histologically differentiating between SCC and MPTT can be difficult, especially in superficial biopsies. Studies have demonstrated the importance of immunohistochemical stains (especially CD34, Ki67, and p53) in assisting subtyping. Complete surgical excision is the mainstay of treatment for both MPTT and SCC, though treatment for advanced forms differ. This patient is currently pending definitive surgical management. Excellent clinical and histopathologic images will be presented.

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Jacob Thomas