Testis and epididymis
Sex cord stromal tumors
Fibromas

Author: Swapnil U. Rane, M.D. (see Authors page)

Revised: 14 July 2017, last major update June 2013

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Testis fibromas

Cite this page: Fibromas. PathologyOutlines.com website. http://pathologyoutlines.com/topic/testisfibroma.html. Accessed October 22nd, 2017.
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:

Unencapsulated and circumscribed appearance

Spindle cells
arranged in
storiform and
herringbone pattern

A: The tumor is well circumscribed with an inconspicuous fibrous capsule and surrounded by atrophic seminiferous tubules (hematoxylin - eosin [H&E] stain x40)
B: Tumor is composed of epithelioid round cells in vague cords and small nests separated by collagen fibers, mimicking a metastatic adenocarcinoma (H&E stain x100)
C: Tumor cells have round oval nuclei with small distinct nucleoli and fine, regularly dispersed chromatin; pale granular cytoplasm with variable sized vacuoles push nuclei to periphery; resemble signet ring cells (H&E stain x400)
D: A few intracytoplasmic eosinophilic hyaline globules can be seen; these eosinophilic globules resemble extracellular collagen bundles (H&E stain x1000)
E and F: 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