Other tumors

Adenomatoid tumor

Last author update: 15 May 2023
Last staff update: 15 May 2023

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PubMed Search: Adenomatoid tumor uterus

Laura Ardighieri, M.D.
Amanda L. Strickland, M.D.
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Cite this page: Ardighieri L, Ayhan A, Strickland AL. Adenomatoid tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/uterusadenomatoid.html. Accessed May 19th, 2024.
Definition / general
  • Benign tumor composed of mesothelium and smooth muscle
Essential features
  • Uncommon benign tumor most frequently seen in the genital tract of both sexes
  • In the uterus, they are commonly asymptomatic
    • Typically present as subserosal or intramural small, solitary nodule
    • Usually an incidental finding in resection specimen for unrelated disease (leiomyoma, adenomyosis, endometrial cancer)
    • Could raise diagnostic difficulties, as morphology may overlap with various differential diagnoses (see Differential diagnosis) (Adv Anat Pathol 2020;27:394)
ICD coding
  • ICD-O: 9054/0 - adenomatoid tumor, NOS
  • Reproductive aged women
    • Mean age is 45 years; range of 24 - 72 years
    • 1.2% of hysterectomy specimens (5% of uterine surgical specimens but true incidence may be higher due to misdiagnosis and missed diagnosis) (Biomed Rep 2013;1:352)
    • Multifocal and diffuse in immunosuppressed patients (Int J Gynecol Cancer 2009;19:242)
  • Neoplastic rather than reactive (based on molecular, clinical and pathological features) (Hum Pathol 2016;48:88)
Clinical features
  • By histopathology
  • Routine hematological and biochemical parameters are within normal limits
  • Occasional anemia and low hemoglobin level because of uterine bleeding
Radiology description
  • Magnetic resonance: small solid uterine masses with homogeneous hypointensity on T2 weighted images and lower enhancement or cystic lesions with inner irregular solid nodules (J Comput Assist Tomogr 2015;39:499)
Prognostic factors
Case reports
  • Surgical removal (hysterectomy or rarely, simple excision)
  • Excision is adequate treatment
Gross description
  • Solitary, small (range of 0.2 - 3.5 cm; average is 2.1 cm), solid nodular, well circumscribed but nonencapsulated, ill defined margins, gray-white-yellow rubbery cut surface
  • Occasionally grossly inconspicuous
  • Rarely diffuse, multifocal, large or predominantly cystic (J Cancer Res Ther 2015;11:967)
  • Large multicystic tumors have a honeycomb, spongy pattern / cysts filled with serous fluid
  • Exophytic serosal component may rarely be seen
Gross images

Contributed by Ayse Ayhan, M.D., Ph.D.

Adenomatoid tumor and leiomyoma

Microscopic (histologic) description
  • Organized in vascular-like, gland-like, complex slit-like and cystic branching spaces; also tubules or combination of above
  • Less commonly cribriform, solid, anastomosing cords, single cells, focal papillary architecture
  • Tubules may contain basophilic secretions
  • Thread-like bridging strands (attenuated cytoplasm that traverse the pseudovascular spaces) (Ann Diagn Pathol 2003;7:273)
  • No mitoses, no necrosis, no atypia
  • Background: hyperplastic smooth muscle
  • Stroma: edematous, inflammatory infiltrate; sometimes lymphoid follicles; lymphocytes or foamy macrophages can be found in the lumina of the tubules
Microscopic (histologic) images

Contributed by Jian-Jun Wei, M.D. and Ayse Ayhan, M.D., Ph.D.

Vascular-like, cystic branching spaces in a background of benign smooth muscle

AE1 / AE3 positive in AT cells

Alcian blue staining secretions

Calretinin and D2-40

Cytology description
  • Flattened, cuboidal epithelioid cells: scant, pale, eosinophilic cytoplasm (may contain vacuoles) with hairy basophilic apical surface
  • Bland, round nuclei, small nucleoli
  • Occasional signet ring-like cells, which are negative for PAS and mucicarmine and may be positive for acidic Alcian blue and colloidal iron
  • No mitotic activity / no cytological atypia
  • Occasional nests of squamoid cells
Negative stains
Electron microscopy description
  • Abundant long, slender microvilli; desmosomes; complex intercellular canalicular system; single layer basement membrane (Cancer 1970;25:171)
Molecular / cytogenetics description
Sample pathology report
  • Uterus, hysterectomy:
    • Adenomatoid tumor (see comment)
    • Comment: This benign entity is composed of mesothelial cells arranged in vascular-like and cystic branching spaces among a background of smooth muscle. The mesothelial cells are positive for calretinin, which supports the diagnosis above.
Differential diagnosis
  • Adenocarcinoma (including signet ring cell carcinoma):
    • Malignant glandular neoplasm, sometimes with signet ring cells (diagnostic pitfall: mesothelial cells may appear signet ring-like)
    • Cytology may be more pleomorphic in adenocarcinoma but not always
    • Cytokeratins are positive (in adenocarcinoma and adenomatoid tumor), mesothelial markers are negative
  • Hemangioma / lymphangioma / peritoneal inclusion cysts:
    • Presence of vascular / lymphatic elements (which are not present in adenomatoid tumor)
    • CD31 and CD34 positive
  • Leiomyoma:
    • Border with adjacent myometrium may be more defined / bulging compared with adenomatoid tumors
    • Absence of mesothelial lining
    • Cytokeratins are negative, smooth muscle markers (SMA, h-caldesmon) are positive
  • Lipoleiomyoma:
  • Well differentiated liposarcoma:
    • Common sites include deep thigh of lower extremity, retroperitoneum, head and neck area, spermatic cord
    • At least focal cytologic atypia typically present
    • Cytokeratins are negative, MDM2 is positive, CDK4 is positive
  • Mesothelioma (benign versus malignant):
    • M > F
    • Strong association with various industrial / environmental / domestic exposures
    • No single marker significantly sensitive or sufficient for mesothelioma
Additional references
Board review style question #1

A 45 year old woman underwent a hysterectomy for symptomatic fibroids. Multiple nodules are identified grossly. A photomicrograph of one of the nodules is included above. Which IHC stain would be the most appropriate to order and would stain positive in the cells of interest?

  1. Calretinin
  2. GMS
  3. MDM2
  4. p16
  5. SOX10
Board review style answer #1
A. Calretinin. Calretinin is the correct answer as it highlights the mesothelial cells in the adenomatoid tumor. All the other answer choices do not highlight the cells of interest.

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Reference: Adenomatoid tumor
Board review style question #2
An adenomatoid tumor is identified in the myomectomy specimen of a 45 year old woman. What is the next best step in management?

  1. 3 cycles of carbo / taxol
  2. External beam radiation
  3. Infertility workup
  4. Nothing, excision is sufficient
  5. Uterine artery embolization
Board review style answer #2
D. Nothing, excision is sufficient. Adenomatoid tumor is a benign, frequently incidentally found tumor with excellent prognosis. There is no evidence that it impairs fertility. Excision is curative and no additional treatment is needed. For these same reasons, all the other choices are incorrect.

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Reference: Adenomatoid tumor
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