Testis & epididymis
Paratesticular tumors
Adenomatoid tumor


Topic Completed: 28 January 2020

Minor changes: 11 September 2020

Copyright: 2002-2020, PathologyOutlines.com, Inc.

PubMed Search: Adenomatoid tumor [title] testis

Sarah Findeis, M.D.
He Huang, M.D., Ph.D.
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Cite this page: Findeis S. Adenomatoid tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testisepidadenomatoid.html. Accessed September 19th, 2020.
Definition / general
Essential features
  • Most common benign paratesticular tumor
  • Usually based in the epididymis and well circumscribed
  • Expresses markers typical of mesothelial origin
ICD coding
  • ICD10: D29.30 - benign neoplasm of unspecified epididymis
Sites
  • Testicular adnexa
Pathophysiology
  • Not known
Etiology
  • Not known
Clinical features
Diagnosis
  • Primarily made histologically
Laboratory
  • Testicular tumor markers: normal
Radiology description
  • Circumscribed, solid paratesticular mass
  • Unable to distinguish benign versus malignant on sonography (Radiology 1997;204:43)
  • Tumors of the tunica may be indistinguishable from a germ cell tumor by imaging
Radiology images

Images hosted on other servers:

Coronal MR

Ultrasound

Prognostic factors
  • Benign neoplasm
Case reports
Treatment
  • Surgical excision
  • Intraoperative frozen section may be helpful to indicate testis sparing surgery
Gross description
Gross images

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Well circumscribed tumor

Frozen section description
  • May be confused for malignant mesothelioma on biopsy; gross correlation often needed
  • Can have atrophic testes with fibrous stromal proliferation (Urology 2004;63:779)
Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Sarah Findeis, M.D.

Interface with testis

Cords and trabeculae pattern

Eosinophilic cells

Calretinin

CK AE1/3



Contributed by Stephanie J. Conrad, M.D., Ming Zhou, M.D. and the Genitourinary Pathology Society (GUPS)

Circumscribed tumor

Dilated cystic spaces

Vacuolated and attenuated epithelium

Bland nuclei

Calretinin

Cytology description
  • Epithelioid, monolayered sheets or clusters of cells with eccentric, vesicular round to ovoid nuclei, granular chromatin and pale / vacuolated cytoplasm (J Cytol 2009;26:30, J Cytol 2013;30:65)
  • Can have a background of naked nuclei as well as stromal cells (Acta Cytol 1989;33:6)
Cytology images

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Moderate cellularity

Monolayered sheets of cells

Negative stains
Electron microscopy description
  • Rich in cytoplasmic organelles and has superficial desmosomes with microvilli (Cancer 1972;30:244)
Molecular / cytogenetics description
Sample pathology report
  • Testicle and spermatic cord, right, radical orchiectomy:
    • Paratesticular adenomatoid tumor, 1.5 cm
    • Margins widely free of tumor (> 5.0 cm)
    • Unremarkable background testis, epididymis and spermatic cord
    • Comment: The tumor is positive for AE1/3, WT1 and calretinin and is negative for SALL4 and inhibin.
Differential diagnosis
Board review style question #1

    Which is true regarding this paratesticular entity which does not involve the testicular parenchyma?

  1. Exclusively identified within men
  2. Malignant transformation occurs in 50% of cases
  3. Most common in the sixth - seventh decade
  4. Rarely identified within the testicular parenchyma
Board review answer #1
D. These tumors are rarely identified within the testicular parenchyma
Explanation: This is an adenomatoid tumor. They can be identified within both sexes. It occurs in the paratesticular region most commonly in the third - fourth decade. The tumor rarely involves the testicular parenchyma. If there is only intraparenchymal involvement, other primary parenchymal lesions need to be ruled out, such as a sex cord stromal tumors or germ cell tumors.

Reference: Adenomatoid tumor

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Board review style question #2
    A 36 year old man presents to his physician with a painless testicular mass. Imaging showed a well circumscribed solid mass arising from the tunica albuginea and not involving the testicular parenchyma. An orchiectomy is performed which shows a 2.0 cm unencapsulated white-tan circumscribed nodule. Histologic examination shows cords and tubules of cuboidal eosinophilic cells with vacuolated cytoplasm in the background of fibrous stroma, which infiltrates into the surrounding testicular tubules. What is the most likely staining pattern for this lesion?

  1. Calretinin +, EMA +, BAP 1+
  2. CK AE1/3 -, CD31 +, CD15 +
  3. OCT3/4 +, CEA+, S100+
  4. Vimentin -, CD99 +, calretinin -
Board review answer #2
A. Calretinin +, EMA +, BAP 1+
Explanation: This is an adenomatoid tumor, which is of mesothelial origin as the staining pattern suggests. The patient presentation of a small painless mass in a patient in the third - fourth decade is typical. Adenomatoid tumors rarely involve the testicular parenchyma and are the most common paratesticular tumor. Microscopic infiltration may be misinterpreted as invasion but may occur and the tumor still has a benign course.


Reference: Adenomatoid tumor

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Board review style question #3
    Which of the immunohistochemical stains, when positive, supports the diagnosis of adenomatoid tumor?

  1. AFP
  2. B72.3
  3. Calretinin
  4. CD34
  5. Inhibin
Board review answer #3
C. Calretinin

Reference: Adenomatoid tumor

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