Testis & paratestis

Nonneoplastic lesions

Smooth muscle hyperplasia

Last author update: 1 September 2014
Last staff update: 26 January 2021

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PubMed Search: Smooth muscle hyperplasia [title]

Swapnil U. Rane, M.D.
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Cite this page: Rane SU. Smooth muscle hyperplasia. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testissmoothmuscle.html. Accessed March 27th, 2023.
Definition / general
  • Benign nonneoplastic smooth muscle hyperplasia involving testicular adnexa around vessels or efferent ducts
  • Epididymis is most common site
  • Can involve rete testis, tunica vaginalis, tunica albuginea, spermatic cord
Etiology & Pathophysiology
  • Exact cause not known
  • Obstruction of epididymis or vas deferens ducts hypothesized to be initiating event
Clinical features
  • Most common presentation is painless scrotal mass of long standing duration
  • May have periodic pain but usually not a prominent feature
  • Suspected clinico - radiologically and confirmed histologically
  • No specific laboratory feature
  • Negative tumor markers for germ cell and sex cord stromal tumors
Radiology description
  • Ultrasound helps delineate the lesion, though it may be difficult to exclude involvement of adjacent testis
  • May appear solid or multicystic
Prognostic factors
  • Benign nonneoplastic lesion
  • No recurrence or progression has been reported
Case reports
  • May be excised for diagnosis and treatment
  • No further treatment required
Gross description
  • Mean 2.5 cm, range 6 mm to 7 cm
  • Discrete or ill defined nodules, fusiform or cordlike masses, thickened or diffusely enlarged paratesticular structures
Gross images

Images hosted on other servers:

Well circumscribed multicystic mass

Microscopic (histologic) description
  • Irregular fascicles of smooth muscle in periductal, perivascular, interstitial or mixed pattern
  • No cohesive interlacing growth pattern of leiomyoma
  • May be associated with secondary myxoid change, calcification, hemorrhage, fibrosis
  • May be associated with ectasia of involved ducts, microscopic adenomatoid tumor, vasitis nodosa
  • No cellular atypia, no mitosis, no necrosis
Microscopic (histologic) images

Images hosted on other servers:

Columnar epididymal type epithelium

Cystic duct

Mass blends with ducts in epididymal tail

Immunohistochemistry & special stains
  • Positive for smooth muscle markers but immunohistochemistry not particularly useful in differential diagnosis
Differential diagnosis
  • Leiomyoma: well circumscribed interlacing fascicles of smooth muscle, which displace rather than encase / invade the adjoining structures
  • Leiomyosarcoma: malignant tumor characterized by high cellularity, mitosis, necrosis and cellular atypia and associated with invasive features
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