Soft tissue tumors - Genital type rhabdomyoma

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Soft tissue tumors

Skeletal muscle

Genital type rhabdomyoma

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 21 February 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

Definition
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● Rare benign tumor with skeletal muscle differentiation in vagina, vulva or cervix, usually in middle aged women and rarely urethra
● Extracardiac rhabdomyomas are divided into adult, fetal, and genital (below) histologic types
● Extracardiac tumors are not associated with tuberous sclerosis

Epidemiology
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● Rarely occurs in males in paratesticular region or epididymis or in the tunica vaginalis of the testis or prostate
● Mean age 42 years

Case reports
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● Infant girl with genital rhabdomyoma of the urethra (Hum Pathol 2012;43:597)
● 17 year old boy with locally invasive tumor (J Pediatr Surg 2007;42:E5)
● 19 year old man with testicular tumor (Mod Pathol 1997;10:608)
● 20 year old man with epididymal tumor (Arch Pathol Lab Med 2000;124:1518)
● 48 year old woman with lower abdominal pain and vaginal bleeding (Hum Pathol 2005;36:433)

Treatment
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● Local excision is curative

Gross description
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● Well circumscribed, solitary, up to 3 cm
● Resembles polyp
● Covered by smooth mucosa

Micro description
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● Submucosal, polypoid, well circumscribed, no capsule
● Haphazard strap-like or round striated muscle fibers in fibrous stroma with dilated vessels
● Cells have abundant eosinophilic cytoplasm with glycogen, cross striations, longitudinal myofibrils
● Nucleus is round, vesicular, central and uniform
● May have bi- or multinucleated cells
● No/rare mitotic figures, no cambium layer, no spider cells, no spindle cells or rhabdomyoblasts, no necrosis, no nuclear pleomorphism

Micro images
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Submucosal proliferation of haphazard skeletal muscle cells with prominent cross striations and fibromyxoid stroma

Epididymis

Cervix (various images)

Positive stains
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● Muscle specific actin and desmin highlight rod-like structures; myoglobin (100%)

Negative stains
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● Keratin, EMA, CD68

Differential diagnosis
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● Botyroid variant of embryonal rhabdomyosarcoma: usually <25 years old with rapidly growing mass, cambium layer, atypia, mitotic activity
● Vaginal polyp: may have atypical cells, but no cross striations

End of Soft tissue tumors > Skeletal muscle > Genital type rhabdomyoma

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