MRI evaluation of the histopathological characteristic of limb soft-tissue aggressive fibromatosis

Abstract

Objective To assess the value of using MRI to evaluate the histopathological characteristic of limb soft-tissue aggressive fibromatosis (AF). Methods The MBI findings and histopathological data of 20 patients with AF were obtained and analyzed. The difference between the different signal regions in AF were compared of signal intensity in T1-weighted images, T2-weighted images and degree of enhancement. The data were processed with paired t test. The histopathology of different signal regions was observed in 6 cases on HE stain and Masson trichromic stain of AF specimen. Results (1) AF predominantly originated from the skeletal muscles (19/20), presenting as Iobulated mass with infiltrative growth(20/20) ;(2) A few claw-shaped neo-arteries(7/7) were delineated in the periphery of the mass in the 3D DCEMRA images as well as the mild tumor staining(7/7) ; (3) Based on the MRI findings, the porenchyma of 20 AF was divided into two distinct regions of structure: region Ⅰ and region Ⅱ. Region Ⅰ presented as hypointensity on both T1-weighted and T2-weighted images and no enhancement after i. v. administration of contrast. Region Ⅱ presented as mild hyperintensity on T2-weighted images and iso- or hypointensity on T1-weighted images and marked enhancement; (4) The signal intensity in T1-weighted images, T2-weighted images and degree of enhancement was 0. 10 ± 0. 02,0. 24 ± 0. 03, and ( 5.22 ± 0.42)% in region Ⅰ , respectively; and 0.79±0.04,3.05±0.08 and(151.5±8.61)% in region Ⅱ, respectively. The differences between region Ⅰ and region Ⅱ were statistically significant of signal intensity in T1-weighted images( t = 67. 37 ), and signal intensity in T2-weighted images( t = 196. 56) and degree of enhancement(t =76. 62) (P <0. 01 ) ; (5) Histologically, AF was composed of fibroblasts, fibrecytes and bundles of collagen fiber. On Massen triehromie stain, region Ⅰ was stained blue, being proven the mature collagen fibers. Region Ⅱ was predominantly composed of fibroblasts, fibrecytes and was not stained. Conclusion The region Ⅰ and region Ⅱ are the characteristic MRI manifestations of AF, and MBI precisely reflects the histopathological and biological feature of the tumor. Key words: Myofibromatosis; Magnetic resonance imaging; Pathology