A locally aggressive proliferating pilar tumor resembling squamous cell carcinoma: A case report and review of the literature

Background: Proliferating Pilar tumors are uncommon dermal lesions that are most commonly found on the scalp. Due to the rarity of the lesion and certain similarities, proliferating pilar tumors are often mistaken for other malignant skin lesions. Certain characteristics can aid in early diagnosis and help guide clinical decision making. We report a case of a large, fungating proliferating pilar tumor that was thought to represent malignancy prior to final surgical pathology results. Case presentation: A 70-year-old female with extensive sun exposure and prior cutaneous malignancies presented with a large fungating, malodorous right parietal scalp mass (Fig. 1) as well as another midline subcutaneous scalp mass. Physical exam and contrast-enhanced CT demonstrated a 9.5cm mass in the right parietal region arising in the skin and demonstrating full-thickness invasion of the scalp without obvious bony invasion, but possible adherence to the periosteum. Punch Biopsy was obtained which was concerning for squamous cell carcinoma. Recommendations were made for wide local excision with likely need for post-operative radiation. Final pathology results were consistent with a proliferating pilar tumor accompanied by a simple pilar cyst. Conclusions: We report a case of a rare, locally aggressive, proliferating pilar tumor. A high-index of suspicion is required as these lesions are rare and easily mistaken for cutaneous malignancy. Judicious work-up as well as careful attention to certain characteristics can allow for early diagnosis, assisting in patient counseling and management.