Extensive Calvarial Reconstruction for Recurrent Scalp Malignant Proliferating Trichilemmal Tumor: Case Report

Abstract Malignant proliferating trichilemmal tumor (MPTT) is a rare cutaneous neoplasm that arises from the external root sheath of the hair follicles, typically affecting sun-exposed areas such as the scalp, neck, and forehead; it is also misdiagnosed due to its resemblance to other skin neoplasms. This report highlights a rare case of a MPTT with repeated local recurrences, despite undergoing wide surgical resections and adjuvant radiotherapy in two different occasions. We present a case of a 42-year-old African − American man diagnosed with a MPTT of the scalp in 2013, which was treated with surgical excision and adjuvant radiotherapy. In the following years, the patient experienced several local recurrences with deeper involvement of the calvarial bone, requiring multiple additional procedures. In 2023, he underwent bifrontal, biparietal, and right temporal craniectomy for complete tumor excision, followed by a second course of radiotherapy and a further scalp reconstruction in early 2024. Subsequent imaging studies revealed no signs of recurrence, and biopsy results confirmed absence of residual tumor. This case exposes an unusually aggressive and treatment-refractory MPPT, which required multiple surgical procedures for wide resection, as well as two complete courses of radiotherapy, to achieve tumor control; these characteristics place this presentation among the most treatment-refractory forms of the disease reported to date. While radiotherapy has been reported as an effective alternative in cases of tumors resistant to surgery, our experience emphasizes the need for a multimodal strategy when recurrence is suspected, whether based on histopathological features or clinical presentation. This underscores the importance of early surgical intervention, multidisciplinary management, and close long-term follow-up in such rare and challenging tumors.