Hagan, M Teresa

BACKGROUND Malignant peripheral nerve sheath tumors (MPNSTs) are malignant tumors that rarely demonstrate heterologous differentiation from angiosarcomatous components. These lesions can be hard to accurately diagnose. OBSERVATIONS A 25-year-old man with neurofibromatosis type 1 and a history of a left lumbar subcutaneous MPNST developed a lung metastasis of only the angiosarcoma component of the MPNST. Prior to H3K27me3 staining of the lung mass, there was no association of the angiosarcoma with the MPNST. Reinterpretation of the lumbar subcutaneous MPNST led to the identification of a previously unrecognized angiosarcomatous portion in that tumor as well. LESSONS This case highlights the importance of using H327me3 staining for accurate diagnosis of biopsies only capturing the heterologous components of MPNST. https://thejns.org/doi/10.3171/CASE251012

ABSTRACT Background Cerebrospinal fluid (CSF) leak after retrosigmoid vestibular schwannoma resection remains a challenging complication. Historically, surgeons reopened the prior retrosigmoid incision for transmastoid repair because the safety of creating a separate postauricular incision was uncertain, with concerns regarding wound breakdown and infection. However, limited data support this practice, and a focused mastoid incision may offer improved access and patient tolerance. This study evaluated wound healing outcomes following transmastoid repair using a new postauricular incision for persistent CSF leak after retrosigmoid surgery in patients without serviceable hearing. Methods We retrospectively reviewed 27 patients who underwent transmastoid repair for persistent postoperative CSF leak after retrosigmoid craniotomy for vestibular schwannoma (2000–2025). Demographics, operative details, timing of leak diagnosis and repair, wound complications, readmissions, antibiotic use, and culture results were analyzed. Results Median age was 48 years (IQR 41–56); 67% were male, and mean BMI was 29.0 kg/m 2 . Mastoid obliteration was performed in 96%, with fat grafting in 93%. A new postauricular incision was used in all cases. Median time to leak diagnosis was 13 days (IQR 4–79), and median time to repair was 2 days (IQR 1–5). One patient (3.7%) developed a superficial wound abscess; no dehiscence or flap necrosis occurred. At median follow‐up of 34 months (IQR 2.9–87.7), all wounds were healed. CSF leak recurred in two patients (7.4%) and three (11.1%) required reoperation. Conclusion A separate postauricular incision for transmastoid CSF leak repair was not associated with increased wound morbidity. Durable wound healing was achieved in all patients, with 93% legal control, supporting this anatomy‐driven approach. Level of Evidence 4