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adenomatoid tumor

Friday 27 February 2004

adenomatoid tumors; "benign mesothelioma"

Definition: Adenomatoid tumor is a benign, relatively rare neoplasm occurring primarily in the genital tract of both genders.

Adenomatoid tumor is a benign mesothelial tumor usually found in the fallopian tube in females and the paratesticular region in males.

Adenomatoid tumours most commonly arise in the genital tract, but occasionally occur in the pleura. They are small and solitary and usually discovered as incidental findings.

Histologically, they are composed of vacuolated epithelioid mesothelial cells forming tubular spaces.

Adenomatoid tumor has groups of cystic spaces with flattened cells. It is a benign tumor of mesothelial origin, and stains positive for mesothelial markers by IHC. It is the most common benign tumor of the fallopian tube. Adenomatoid tumor is benign.

Images

- uterine adenomatoid tumor or tubal adenomatoid tumor

- paratesticular adenomatoid tumor / epididymal adenomatoid tumor

- adrenal adenomatoid tumor

Localization

- epididymal adenomatoid tumor
- adenomatoid tumor of the tunica albuginea
- adenomatoid tumor of the testicle
- adenomatoid tumor of the ovary
- adenomatoid tumor of the myometrium
- adenomatoid tumor of the fallopian tube
- adenomatoid tumor of the parafallopian region
- adenomatoid tumor of the mediastinum (14707875)
- adenomatoid tumor of the adrenal gland (14506647)
- pleural adenomatoid tumor

Synopsis

- cystic spaces lined by flattened or cuboidal epithelial cells
- walls of the cysts: proliferation of small canalicular structures lined by round to polygonal epithelioid cells with vacuolated eosinophilic cytoplasm
- +/- infarction (14707867)
- fibrous tissue
- numerous slit-like and pseudotubular spaces
- thread-like bridging strands crossing the pseudotubular spaces (14571427)

Immunohistochemistry

Adenomatoid tumor is also called ‘benign mesothelioma’ and stains similarly to mesothelial cells: positive for calretinin, WT-1, D2-40 and cytokeratin AE1/AE3. It may stain positive for ER/PR as well.

- AE1/AE3 cytokeratin+
- CK5/CK6 cytokeratin+
- calretinin+
- CK7-
- CK20-
- alpha-fetoprotein-
- CD31-
- carcinoembryonic antigen-
- MOC-31-
- chromogranin-

Electron microscopy

- numerous long microvilli on the cell surface and abundant tonofilaments/desmosomal plaques in the tumor cells, characteristic of mesothelial cells

Differential diagnosis

- lymphangioma

  • Adenomatoid tumor resembles lymphangioma.
  • They both stain positive for D2-40. D2-40 stains lymphatic tissue, and also stains cells of mesothelial origin, such as the adenomatoid tumor and mesothelioma.
  • Adenomatoid tumor stains positive for calretinin, WT-1, D2-40 and cytokeratin AE1/AE3. Lymphangioma would also show lymphocytes in the cyst spaces.