Treatment and Clinical Course of a Massive Malignant Proliferating Trichilemmal Tumor

Summary: Malignant proliferating trichilemmal tumors (MPTTs) are rare, rapidly growing lesions often originating from a small cyst on the scalp. We present a case of a 61-year-old woman who presented due to concern for increased bleeding from an extremely large cystic mass on her posterior scalp, measuring 22 × 10 × 15.2 cm. She reported that the mass began as a cyst approximately 10 years before presentation but had grown rapidly in the last 3 years, causing her significant pain. Dermatopathology revealed a suspected diagnosis of an MPTT based on a punch biopsy. An interdisciplinary surgical team was organized, including otolaryngology, neurosurgery, and plastic surgery, to pursue surgical excision and reconstruction of her complex mass. Intraoperative histopathology demonstrated cytological atypia, necrosis, and infiltrative growth, confirming the suspected diagnosis of an MPTT. Following successful tumor removal, her scalp defect was closed using a latissimus dorsi free flap. Eleven months postoperatively, the patient’s scalp was well-healed, with no signs of tumor recurrence. Our case is unique due to the tumor’s exceptional size, malignant histology, and the patient’s delay in seeking treatment despite its burdensome size and location. As seen in our patient, an initially benign cyst can rapidly progress to a large tumor, causing pain and distress. Additionally, such large masses can cause significant reactive lymphadenopathy. MPTTs carry a small but significant risk of local recurrence and metastasis. Removal of such large tumors, particularly those on the scalp, necessitates a well-coordinated effort from a multidisciplinary surgical team to ensure optimal excision, reconstruction, and patient relief.