OBJECT: The completeness of meningioma resection depends on the resection of 
dura mater invaded by the tumor. The pathological changes of the dura around the 
tumor can be interpreted by evaluating the dural tail sign (DTS) on MRI studies. 
The goal of this study was to clarify the pathological characteristics of the 
DTSs, propose a classification based on the histopathological and radiological 
correlation, and identify the invasive range of tumor cells in different types 
of DTS.
METHODS: The authors retrospectively reviewed 179 patients with convexity 
meningiomas who underwent Simpson Grade I resection. All patients underwent an 
enhanced MRI examination preoperatively. The convexity meningiomas were 
dichotomized into various subtypes in accordance with the 2007 WHO 
classification of tumors of the CNS, and the DTS was identified based on the 
Goldsher criteria. The range of resection of the involved dura was 3 cm from the 
base of the tumor, which corresponded with the length of DTS on MRI studies. 
Histopathological examination of dura at 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 cm 
from the base of the tumor was conducted, and the findings were correlated with 
the preoperative MRI appearance of the DTS.
RESULTS: A total of 154 (86%) of 179 convexity meningiomas were classified into 
WHO Grade I subtype, including transitional (44 [28.6%] of 154), meningothelial 
(36 [23.4%] of 154), fibrous (23 [14.9%] of 154), psammomatous (22 [14.3%] of 
154), secretory (10 [6.5%] of 154), and angiomatous (19 [12.3%] of 154). The 
other 25 (14%) were non-Grade I (WHO) tumors, including atypical (12 [48%] of 
25), anaplastic (5 [20%] of 25), and papillary (8 [32%] of 25). The DTS was 
classified into 5 types: smooth (16 [8.9%] of 179), nodular (36 [20.1%] of 179), 
mixed (57 [31.8%] of 179), symmetrical multipolar (15 [8.4%] of 179), and 
asymmetrical multipolar (55 [30.7%] of 179). There was a significant difference 
in distribution of DTS type between Grade I and non-Grade I tumors (p = 0.004), 
whereas the difference was not significant among Grade I tumors (0.841) or among 
non-Grade I tumors (p = 0.818). All smooth-type DTSs were encountered in Grade I 
tumors, and the mixed DTS (52 [33.8%] of 154) was the most common type in these 
tumors. Nodular-type DTS was more commonly seen in non-Grade I tumors (12 [48%] 
of 25). Tumor invasion was found in 88.3% (158 of 179) of convexity meningiomas, 
of which the range of invasion in 82.3% (130 of 158) was within 2 cm and that in 
94.9% (150 of 158) was within 2.5 cm. The incidence of invasion and the range 
invaded by tumor cells varied in different types of DTS, and differences were 
statistically significant (p < 0.001).
CONCLUSIONS: Nodular-type DTS on MRI studies might be associated with non-Grade 
I tumors. The range of dural resection for convexity meningiomas should be 2.5 
cm from the tumor base, and if this extent of resection is not feasible, the 
type of DTS should be considered. However, for skull base meningiomas, in which 
mostly Simpson Grade II resection is achieved, the use of this classification 
should be further validated. The classification of DTS enables the surgeon to 
predict preoperatively and then to achieve the optimal range of dural resection 
that might significantly reduce the recurrence rate of meningiomas.