PMC6180818_01
(a) Axial unenhanced T
1 weighted MRI shows a pelvic mass primarily isointense to muscle (arrowheads) with few areas of high signal intensity. (b) Sagittal T
2 weighted MRI displays major high signal intensity interspersed with swirled or layered strands of lower signal intensity. (c,d) Axial T
2 weighted and fat-suppressed T
2 weighted images show the same swirling appearance with lack of major adipose components. Marked compression of the bladder is notable and mild displacing of vaginal and anal canal is shown. (e) Coronal post-contrast T
1 weighted MRI with fat suppression reveals the swirling pattern of remarkable enhancement within the tumour and infiltration of right elevator ani muscle (arrow). No signs of internal obturator muscle infiltration were observable. (f,g) Diffusion weighted imaging sequences (B0-B1000) demonstrate heterogeneous high signal. (h) ADC shows quite homogeneous hyperintense signal on ADC map. ADC, apparent diffusion coefficient.
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B0 and B1000 sequences; apparent diffusion coefficient (ADC) mapping showed a high value in the tumour (Figure 1). Based on peculiar localization and MRI findings, radiologists suggested the diagnosis of AA.
Locally infiltrative growth of bland fibro-myofibroblastic cells with characteristic thick-walled blood vessels and a focally myxoid stroma into adipose tissue (HE, 5x).
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Tru-Cut 16G needle with a perineal approach was performed; pathologists definitively confirmed the diagnosis of AA. The tumour histologically consisted of spindle cells in a myxoid stroma, containing a mixture of thick- and thin-walled blood vessels with interposition of normal fat tissue (Figure 2).
6-month MRI control scan after hormonal replacement therapy withdrawal. (a) Axial T
2 weighted image shows a great reduction in size of the tumour (arrowheads). (b,c) Axial fat-suppressed T
2 weighted images show loss of main hyperintensity and "finger-like" extension still notable in the right ischiorectal fossa (arrow). (d) Coronal T
2 weighted image shows main loss of swirling appearance. (e,f) Axial and coronal post-contrast T
1 weighted images display decrease in internal vascularization. Bladder compression is no longer evident. Signs of elevator ani muscle infiltration are still notable (arrowhead). (g) Diffusion weighted imaging (B1000) shows a soft hyperintense signal. (h) On apparent diffusion coefficient map, the lesions confirm its quite homogeneous hyperintensity.
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On DWI sequences, AA remained hyperintense on both B0 and B1000 images and ADC map (Figure 3).