Aggressive Angiomyxoma with Diffusion-Weighted Magnetic Resonance Imaging and Dynamic Contrast Enhancement: A Case Report and Review of the Literature
In July 2011, a 51-year-old woman presented to her general practitioner with an incidentally discovered renitent mass in the internal part of the left buttock. Initial ultrasound (US) showed a well-circumscribed mass initially evoking a lipoma. Due to the large volume of the mass, the patient was referred to our hospital.\nThe patient did not have any specific medical, personal, or familial history. Her treatment included hormone replacement therapy. Rectal examination palpated the renitent mass. She was otherwise asymptomatic with a performance status score of 0 on the WHO scale. Laboratory findings were unremarkable. US showed a superficial, soft, hypoechoic, well-limited, solid mass. US-guided biopsy showed mature adipocytes associated with nonatypical fibroblast-like cells. Endorectal US showed a 39-mm hypoechoic lesion distant from the internal and external sphincters.\nMRI showed a bulky perineal and intrapelvic tumour displacing rather than infiltrating the vagina, anal canal, and rectal structures. The mass was well limited, hourglass-shaped and had a maximum diameter of 11 cm (fig. ). On T1-weighted imaging, the tumour was isointense relative to muscle. T2-weighted imaging showed typical high signal intensity with layered strands of lower signal intensity and swirled architecture. Finger-like projections into the underlying adipose tissue were observed. A fat linear structure of high signal intensity on T1- and T2-weighted images was present inside the mass. Its significance was unknown, perhaps representing neighbouring tissues trapped when the tumour was growing. After intravenous contrast injection, the mass was greatly and heterogeneously enhanced, exhibiting a layered pattern (fig. ). The tumour's DCE analysis showed a progressive curve without plateau or washout. Regions of interest located in the layers demonstrated the same profile curves of progressive enhancement with variable intensity.\nDW-MRI sequences (fig. ) showed heterogeneous high signal intensity on b0 and b1000 sequences. Typical architecture was only observed on b0 sequences. Apparent diffusion coefficient (ADC) mapping showed a high value in the tumour, estimated at 2 × 10−3 (±0.15) mm2/sec.\nThus, MRI was highly suggestive of AA. It also showed disease extension, notably through the pelvic diaphragm, which made a combined transperineal and laparoscopic abdominopelvic approach necessary. Before surgery, the examination under general anesthesia showed that the mass was soft, renitent, and seemed to come from the pelvic cavity through the levator ani muscles. Tumour excision was monobloc and macroscopically complete, without any rectal or vaginal resection or tumour capsular rupture. The postoperative course was uneventful.\nMacroscopic examination of the surgical specimen showed a firm, partly circumscribed tumour measuring 16 × 12 × 6.5 cm. A cut section showed a homogeneous, glistening, and gelatinous appearance without any hemorrhagic or necrotic areas. Microscopic analysis showed a monotonous hypocellular proliferation of small nonatypical stellate-shaped cells arranged in a myxoid stroma, along with numerous, variably sized vessels. No mitosis or necrosis could be seen. In its periphery, the proliferation infiltrated the nontumour adipose tissue, and resection margins were focally involved by the tumour cells. Immunohistochemical analysis showed strong expression of CD34, and estrogen and progesterone receptors by tumour cells, without expression of desmin, CD117, β-catenine, and MDM2, nor epithelial (pancytokeratin, EMA), smooth muscle (α-smooth actin, H-caldesmon), and Schwann cell (PS100) markers. The final diagnosis was pelvi-perineal AA.\nAfter surgery, no adjuvant treatment was given, and the patient was regularly monitored clinically and radiologically. At her last visit, in October 2012, more than 1 year after the diagnosis, the patient was alive with an excellent performance status and without any recurrence of the disease on pelvic DW-MRI.