Uterus
Other tumors
Adenomatoid tumor
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PubMed Search: Adenomatoid tumor uterus
Table of Contents
Definition / general | Essential features | ICD coding | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Laboratory | Radiology description | Prognostic factors | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Sample pathology report | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Ardighieri L, Ayhan A, Strickland AL. Adenomatoid tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/uterusadenomatoid.html. Accessed September 22nd, 2023.
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
Epidemiology
- 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)
Sites
- In the female genital tract: uterus (outer myometrium, close to cornu, subserosal or intramural) / fallopian tube / ovarian hilus / broad ligament (J Obstet Gynaecol India 2015;65:255)
- May rarely involve the superficial myometrium; eventually may be present in endometrial curettings (Int J Gynecol Pathol 1986;5:69)
- In the male genital tract: epididymis / tunica albuginea / spermatic cord / tunica vaginalis, testis and prostate
- Extragenital tumors are rare
- Adrenal glands (World J Surg Oncol 2014;12:377)
- Pleura (Respir Med 2015;109:931)
- Mesentery, mesocolon, peritoneum (APMIS 2008;116:1016)
- Omentum (Pathol Int 2011;61:681)
- Appendix (J Obstet Gynaecol Res 2003;29:234)
- Liver (BMJ Case Rep 2014;2014:bcr2014207687)
- Mediastinum (Case Rep Pathol 2016;2016:6898526, Gen Thorac Cardiovasc Surg 2016;64:47)
- Lymph node (Mayo Clin Proc 2003;78:350)
- Heart (Cardiovasc Pathol 2002;11:181)
- Pancreas (Mod Pathol 2003;16:613)
- Umbilicus (Arch Pathol Lab Med 2003;127:e303)
- Small intestine (Int J Surg Pathol 2015;23:94)
- Gastrointestinal tract and liver (Histopathology 2022;80:348)
Pathophysiology
- Neoplastic rather than reactive (based on molecular, clinical and pathological features) (Hum Pathol 2016;48:88)
Etiology
- Derived from mesothelium
- Ultrastructural and immunohistochemical studies support its mesothelial nature (Int J Gynecol Pathol 2002;21:34)
- Pluripotent Müllerian mesenchymal stem cells (Pathol Res Pract 1999;195:605)
Clinical features
- Most are asymptomatic / incidental with nonspecific symptoms (Int J Gynecol Pathol 2002;21:34)
- Occasional larger examples may be symptomatic
- Vaginal bleeding, abdominal pain, irregular menses, menorrhagia
- Diffuse variants in immunosuppressed and in hepatitis C (HCV) / HIV infected patients (Int J Gynecol Cancer 2009;19:242, Ann Pathol 2008;28:308, Int J Gynecol Pathol 2003;22:198)
- May occasionally occur with peritoneal inclusion cysts (previously termed benign cystic mesothelioma) (Histopathology 1996;29:375)
Diagnosis
- By histopathology
Laboratory
- 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
- Benign tumor with excellent prognosis
- No evidence that these tumors impair fertility (Kurman: Blaustein's Pathology of the Female Genital Tract, 7th Edition, 2019)
Case reports
- 26 year old woman with multicentric adenomatoid tumors involving uterus, ovary and appendix (J Obstet Gynaecol Res 2003;29:234)
- 38 year old woman who underwent laparoscopic excision (enucleation) of a uterine adenomatoid tumor and a coexisting ovarian teratoma (J Nippon Med Sch 2017;84:139)
- 41 and 58 year old women with ovarian adenomatoid tumors mimicking malignancy (BMC Womens Health 2022;22:547)
- 44 year old woman with laparoscopically resected uterine adenomatoid tumor with coexisting endometriosis (J Minim Invasive Gynecol 2011;18:257)
- 44 year old woman with giant cystic adenomatoid tumor of the uterus (J Obstet Gynaecol 2012;32:407)
- 48 year old woman with synchronous adenomatoid tumor of uterus and benign cystic mesothelioma (Medicine (Baltimore) 2019;98:e15746)
- 51 year old woman with incidental 3 cm white-tan subserosal nodule (Case #232)
Treatment
- 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
Positive stains
- Cytokeratins: AE1 / AE3, CAM5.2, CK7, CK8, CK18, CK19 (CK5/6 can also be positive)
- Calretinin, D2-40 (Mod Pathol 2009;22:1228)
- WT1 (Int J Gynecol Pathol 2004;23:123)
- HMBE
- Vimentin
- GLUT1 (cytoplasmic)
- Rarely weak / focal ER and PR (Appl Immunohistochem Mol Morphol 2012;20:173)
- Desmin, smooth muscle actin (smooth muscle components)
- References: Am J Clin Pathol 1981;76:627, Arch Pathol Lab Med 1985;109:1049, J Pathol 1986;148:327, Int J Gynecol Pathol 1996;15:146, Int J Gynecol Pathol 2002;21:34, Crum: Gynecologic and Obstetric Pathology, 1st Edition, 2015
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
- Uniform, nonrandom pattern of X chromosome inactivation, consistent with monoclonality (Hum Pathol 2016;48:88)
- TRAF mutation identified in all tested adenomatoid tumors (Mod Pathol 2018;31:660)
- TRAF mutation may be helpful in distinguishing adenomatoid tumor from malignant mesotheliomas (Hum Pathol 2021;111:59)
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:
- 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:
- Presence of adipose tissue instead of mesothelial lined spaces
- Smooth muscle actin positive
- 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?
- Calretinin
- GMS
- MDM2
- p16
- 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
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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?
- 3 cycles of carbo / taxol
- External beam radiation
- Infertility workup
- Nothing, excision is sufficient
- 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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