Testis & epididymis
Sex cord-stromal tumors
Fibroma-thecoma


Topic Completed: 1 June 2013

Minor changes: 10 September 2020

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PubMed Search: Testis fibromas

Swapnil U. Rane, M.D.
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Cite this page: Rane S. Fibroma-thecoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testisfibroma.html. Accessed September 19th, 2020.
Definition / general
  • Rare, benign behavior
  • Ages 21 - 74 years, painless testicular masses
  • Sex cord stromal tumors composed of spindle, oval or round cells producing collagen
  • Cellular fibromas have scanty collagen
Terminology
  • Synonyms:
    • Benign gonadal stromal tumor - spindle fibroblastic type
    • Diffuse stromal form of gonadal stromal tumor
    • Fibroma of gonadal stromal origin
    • Incompletely differentiated gonadal stromal tumor
    • Myoid gonadal stromal tumor with epithelial differentiation
    • Stromal tumor resembling fibroma
    • Testicular fibroma
    • Testicular stromal tumor with myofilaments
    • Theca cell tumor
    • Thecoma-like Sertoli cell tumor
    • Unclassified sex cord stromal tumor with a predominance of spindle cells
Epidemiology
  • Rare tumor
  • Occurs in third or fourth decade of life
Etiology
  • Associated with Gorlin syndrome (nevoid basal cell carcinoma syndrome, J Pediatr Surg 2010;45:E1), abnormalities of PTCH gene
Clinical features
  • Commonly presents as slowly increasing testicular mass
  • Hormonal changes are extremely uncommon
  • Clinically benign with no reported recurrences or metastases
Case reports
Treatment
  • Orchidectomy
  • Testicular sparing surgery has limited role in large tumors or patients age 30+ years
Gross description
  • Tumor is well circumscribed, rarely encapsulated
  • Usually 0.8 to 7cm
  • Yellow white to white, firm with no hemorrhage or necrosis
Gross images

Images hosted on other servers:

Various images

Microscopic (histologic) description
  • Circumscribed but unencapsulated
  • Fusiform spindle cells arranged in fascicles or storiform pattern in collagenized stroma with small blood vessels
  • Herringbone pattern may be seen
  • Variable cell density, variable collagen
  • Usually scanty mitoses
  • May be infiltrative and entrap seminiferous tubules; this feature has no impact on tumor behavior
  • Usually no Sertoli, granulosa, sex cord types present but may have minor aggregates of other sex cord cells (Arch Pathol Lab Med 1999;123:391)
  • If > 1 microscopic focus of other sex cord stromal cells, classify as mixed or unclassified as these tumors have metastatic potential unlike the classical fibroma
Microscopic (histologic) images

Images hosted on other servers:

Well circumscribed,
inconspicuous
fibrous capsule;
surrounded by
atrophic seminiferous
tubules

Epithelioid round
cells in vague cords
and small nests
separated by collagen fibers

Round nuclei
with fine, dispersed
chromatin; pale
granular cytoplasm

Intracytoplasmic
eosinophilic
hyaline globules;
resemble extracellular
collagen bundles

Tumor cells were immunoreactive for vimentin (E) and CD99 (F)

Negative stains
Electron microscopy description
  • Fibroma cells resemble both fibroblasts and myofibroblasts
  • Have desmosomes like Sertoli and granulosa cells
Molecular / cytogenetics description
  • Although loss of heterozygosity at 9q22.3 (PTCH locus) is observed in 40% of sporadic ovarian thecoma - fibromas, only one case in testis has been reported (J Pediatr Surg 2010;45:E1)
Differential diagnosis
  • Fibrosarcoma: malignant tumor with infiltration, cytological atypia, frequent mitoses, necrosis
  • Leiomyoma and other myoid gonadal stromal tumors: positive for muscle markers, negative for inhibin and other sex cord stromal markers
  • Neurofibroma: patchy S100+, negative for sex cord stromal markers
  • Nodular and profuse fibrous proliferation: less cellular, more inflammatory cells
  • Solitary fibrous tumor: CD34+, tends to arise from extratesticular tissues like tunica albuginea, tunica vaginalis, gubernaculum, not testicular stromal cells
  • Unclassified sex cord stromal tumors: show more than focal incomplete Sertoli cell differentiation, strong S100+ is useful stain
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