Takami, Hirokazu

Abstract Central nervous system hemangioblastoma (CNS HGB) is a rare neoplasm. Sporadic and von-Hippel Lindau (VHL)-associated forms exist. Predicting tumor growth is difficult, making the indication for intervention challenging. A retrospective analysis of consecutive, neurosurgically managed CNS HGB at Mayo Clinic spanning 1988–2018 was performed to clarify their characteristics. 117 sporadic and 67 VHL HGBs were reviewed. 9 sporadic lesions (8 cases) and 80 VHL lesions (35 cases) had tumor size data at ≥4 follow-up time-points beyond 1 year. The median follow-up was 8.0 years. No statistical difference existed between sporadic and VHL lesions regarding growth speed or growth latency (period of time without growth). Symptomatic lesions showed faster growth than asymptomatic lesions (2.79 vs 0.59 cm3/month, p=0.005). Solid and cystic portions often showed different growth patterns in cases harboring both (66.7%). Cyst growth was faster than solid portions (1.22 vs 1.05cm3/month, p=0.009) and growth latency was longer in the latter (15.2 vs 18.5%, p=0.25). Lesions’ growth were classified as linear (7), exponential (49), cubic (regressed to cubic function curve, 7), saltatory (19) and no-growth (7) patterns. Growth latency often existed in growing lesions (27-out-of-64 linear/exponential/cubic lesions, 57.8%), being average 8.3% of follow-up time. Contrarily, although saltatory lesions grew slower than exponential lesions (p=0.03), their overall growth speed was comparable to linear/cubic lesions (0.67cm3/month), and 9-out-of-19 showed growth surges at their ends. Growth speed at each follow-up roughly depended on the tumor size in cubic regression (R2=0.52). However, whereas total 18/821 time-point lesions showed rapid growth (≥1cm3/m, 2.2%), relatively small lesions (≤2cm3) also occasionally showed rapid growth (5/687, 0.73%). Not all large (>5cm3) lesions grew rapidly (8/62, 12.9%). These results revealed while symptomatic/large/cystic lesions tend to grow more rapidly, HGB behavior is difficult to predict, which stresses the importance of careful follow-up.

Glioblastoma (GBM) of the internal auditory canal (IAC) is exceedingly rare, with only 3 prior cases reported in the literature. The authors present the fourth case of cerebellopontine angle (CPA) and IAC GBM, and the first in which the lesion mimicked a vestibular schwannoma (VS) early in its natural history. A 55-year-old man presented with tinnitus, hearing loss, and imbalance. MRI identified a left IAC/CPA lesion measuring 8 mm, most consistent with a benign VS. Over the subsequent 4 months he developed facial weakness. The tumor grew remarkably to 24 mm and surgery was recommended; the main preoperative diagnosis was malignant peripheral nerve sheath tumor (MPNST). Resection proceeded via a translabyrinthine approach with resection of cranial nerves VII and VIII, followed by facial-hypoglossal nerve anastomosis. Intraoperative frozen section suggested malignant spindle cell neoplasm, but final histopathological and molecular testing confirmed the lesion to be a GBM. The authors report the first case in which absence of any brainstem interface effectively excluded a primary parenchymal tumor, in particular GBM, from the differential diagnosis. Given the dramatic differences in treatment and prognoses between malignant glioma and MPNST, this case emphasizes the importance of surgical intervention on an aggressively growing lesion, which provides both the best probability of local control and the critical tissue diagnosis.