General
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• Infiltrative, hypocellular and bland myxoid lesion of perineum and pelvis, much less common in males than females (Am J Clin Pathol 1995;104:391, Stanford University)

Epidemiology
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• Usually adults, but pediatric cases have been reported (Pediatr Dev Pathol 2003;6:187)

Clinical features
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• Slow-growing painless mass, months to years of duration
• Infiltration of deep tissues may occur
• May simulate an inguinal hernia (Asian J Androl 2007;9:723)
• High incidence of local recurrence (Int J Gynecol Cancer 2010;20:303)

Case reports
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• 64 year old man with clinical hydrocele (Case Rep Med 2009;2009:157624)

Clinical images
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Marked swelling

Scrotal mass

Gross description
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• Irregular and infiltrative borders
• Gelatinous, mucoid cut surface
• Tumor size 3-60 cm (usually > 5 cm)

Gross images
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Gelatinous cut surface

Ill-defined mass

Micro description
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• Hypocellular, stellate / spindle stromal cells with delicate cytoplasmic processes
• Prominent myxoid (mucicarmine positive) to collagenous stroma
• Abundant small to medium-sized blood vessels, many with hypertrophy / hyalinization (Am J Surg Pathol 1992;16:1059)
• Extravasation of erythrocytes is common
• No atypia or significant mitotic activity

Micro images
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Thick walled vessels, myxoid to collagenous stroma

Delicate vessels and myxoid stroma

CD34+

Trichrome+

Prominent myxoid stroma

Spindle cells

Variable sized vessels

Perivascular spindled cells

Vimentin+

CD34+

Scattered PR+

Vulvar tumor

Positive stains
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• Vimentin, CD34
• Variable ER, PR (Ann Diagn Pathol 2006;10:197) and androgen receptors (Int J Urol 2003;10:672)

Negative stains
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• Desmin, S100 and CD68
• Muscle specific actin and alpha smooth muscle actin are negative or variable

Molecular description
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• HMGA2 rearrangements in 1/3 (Genes Chromosomes Cancer 2007;46:981)

Differential diagnosis
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• Superficial (cutaneous) angiomyxoma: well-defined borders, nodular / multinodular pattern of growth
• Angiomyofibroblastoma: hypercellular areas, plump neoplastic cells, perivascular accentuation of stromal cells and edematous (not myxoid) stroma

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