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This is a rare and benign neoplasm, often found as an incidental finding with removal of organs such as a uterus or fallopian tube. Although benign, these tumors may have an alarming appearance and may be mistaken histopathologically for a cancer.


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MR appearance of adenomatoid tumor of the uterus.

Mitsumori A, Morimoto M, Matsubara S, Yamamoto M, Akamatsu N, Hiraki Y.

Department of Radiology, Himeji Red Cross Hospital, Hyogo, Himeji-City, Japan.
J Comput Assist Tomogr. 2000 Jul-Aug;24(4):610-3. Abstract quote  

Reports on the radiological findings of adenomatoid tumor of the uterus are rare, and preoperative diagnosis is very difficult. To our knowledge, there have been no reports concerning the MR findings of adenomatoid tumor of the uterus.

We report two cases of uterine adenomatoid tumor that showed the characteristic features of leiomyoma on MR images.


Adenomatoid tumor of the adrenal gland: a clinicopathologic study of 3 cases.

Garg K, Lee P, Ro JY, Qu Z, Troncoso P, Ayala AG.

Department of Pathology, Health Science Center, University of Texas, Houston, TX 77030-4009, USA.
Ann Diagn Pathol. 2005 Feb;9(1):11-5. Abstract quote  

Adenomatoid tumors are relatively uncommon benign neoplasms of mesothelial origin, usually occurring in the male and female genital tracts. Rare extragenital adenomatoid tumors have been identified in the adrenal glands, heart, mesentery, pleura, and lymph nodes. In the adrenal gland, adenomatoid tumors may pose a diagnostic challenge. The differential diagnosis includes adrenocortical carcinoma and metastatic carcinoma, especially signet ring cell carcinoma. Because of its glandular pattern, an adenomatoid tumor may be confused with an adenocarcinoma.

We present 3 cases of adrenal adenomatoid tumors, including one with a concurrent large hemorrhagic vascular adrenal cyst. The adenomatoid tumors were unilateral, appeared solid and white, and varied from 1.7 to 4.2 cm in diameter. They occurred in 3 male patients aged 33, 33, and 46 years. One patient presented with abdominal pain due to the presence of a concurrent large adrenal cyst. The tumor was an incidental radiological finding in another case and was discovered during the course of a workup for hypertension in the third case. The light microscopic appearances were consistent with those of typical adenomatoid tumors. Immunohistochemical stains for calretinin and cytokeratin 5/6 were positive, confirming the tumors' mesothelial origin. Ultrastructural studies performed in 2 cases revealed microvilli and desmosomes. Follow-up showed no evidence of recurrence or metastasis.

In our experience, the key to the diagnosis of this rare benign tumor is to consider adenomatoid tumor in the differential diagnosis of any glandular tumor occurring in the adrenal gland.

Adenomatoid tumor of the adrenal gland with micronodular adrenal cortical hyperplasia.

Chung-Park M, Yang JT, McHenry CR, Khiyami A.

Department of Pathology and Surgery, Case Western Reserve University at Metro Health Medical Center, Cleveland, OH 44109-1998, USA.
Hum Pathol. 2003 Aug;34(8):818-21 Abstract quote.  

We report a case of an adenomatoid tumor (AT) of an adrenal gland with micronodular adrenal cortical hyperplasia (ACH). A 51-year-old man was found to have newly developed hypertension with clinical evidence of primary aldosteronism.

A computerized tomogram of the abdomen revealed a solitary mass in the right adrenal gland. He underwent a right adrenalectomy for a presumptive clinical diagnosis of a solitary aldosterone-producing adrenal cortical adenoma. On histopathologic examination, the adrenal gland demonstrated an AT, diagnosed by the characteristic histological features, immunohistochemical stain results, and electron microscopic findings. The surrounding adrenal cortex showed multiple small hyperplastic cortical nodules. After the adrenalectomy, the patient's blood pressure normalized.

Primary AT of the adrenal gland coexisting with micronodular ACH associated with hypertension has not been previously reported.

Adenomatoid tumor of the adrenal gland: a clinicopathologic study of five cases and review of the literature.

Isotalo PA, Keeney GL, Sebo TJ, Riehle DL, Cheville JC.

Department of Pathology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Am J Surg Pathol. 2003 Jul;27(7):969-77 Abstract quote.  

We report the clinicopathologic, immunophenotypic, DNA ploidy, and MIB-1 proliferative findings of five adenomatoid tumors of the adrenal gland. All patients were male, and tumors were incidental radiologic, surgical, or autopsy findings. Mean patient age at diagnosis was 41 years (range 31-64 years). The tumors ranged from 1.2 to 3.5 cm (mean 2.8 cm; median 3.2 cm) in greatest dimension, and all originated within the adrenal gland.

The tumors were composed of anastomosing variably sized tubules lined by epithelioid as well as flattened cells. Signet-ring-like cells were present in all cases. The previously described histologic patterns of adenomatoid tumor, adenoid, angiomatoid, cystic, and solid, were observed, and each tumor contained multiple histologic patterns. In three of five cases, there was extra-adrenal extension of tumor into periadrenal adipose tissue. All adenomatoid tumors infiltrated the adrenal cortex, and in four cases the adrenal medulla was involved. All tumors exhibited strong immunoreactivity for calretinin, cytokeratins AE1/AE3, and CAM 5.2, cytokeratin 7, and vimentin. Tumors showed weak and focal immunoreactivity for cytokeratin 5/cytokeratin 6 and were negative for CD15, CD31, CD34, cytokeratin 20, MOC31, and polyclonal carcinoembryonic antigen. Ploidy analysis using Feulgen-stained sections and image analysis showed that three tumors were diploid and two were tetraploid. Tumors exhibited low MIB-1 proliferative activity, ranging from 0.2% to 2.7% (mean 1.6%). In three cases with clinical follow-up, no recurrence or metastases occurred.

Adrenal gland adenomatoid tumors are morphologically and immunophenotypically identical to adenomatoid tumors of the genital tract and appear benign.


Extragenital adenomatoid tumor of a mediastinal lymph node.

Isotalo PA, Nascimento AG, Trastek VF, Wold LE, Cheville JC.

Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 First St SW, Rochester, Minn 55905, USA.

Mayo Clin Proc. 2003 Mar;78(3):350-4 Abstract quote.  

Adenomatoid tumors are benign neoplasms found predominantly in male and female genital tracts. Rare extragenital adenomatoid tumors have been discovered that involve serosal surfaces and nonmesothelial-lined organs such as adrenal glands. Since the discovery of adenomatoid tumors, their histogenetic origin has been debated.

Many researchers support a mesothelial cell origin for adenomatoid tumors because these tumors characteristically express a mesothelial phenotype. Tumor derivation from primitive pluripotent mesenchymal cells and coelomic epithelium also has been suggested because of the anatomical distribution of the tumors. Despite their characteristic mesothelial phenotype and histological appearance, adenomatoid tumors have an extensive differential diagnosis that includes vascular neoplasms, malignant mesothelioma, germ cell tumors, and metastatic adenocarcinoma. Recognition of these tumors may be especially difficult when examined at frozen section and when adenomatoid tumors are encountered in rare extragenital sites. We describe an adenomatoid tumor of a mediastinal lymph node that was found incidentally during a redo Collis-Nissen gastroplasty. On frozen section examination, this tumor was misinterpreted as metastatic adenocarcinoma.

The hematoxylin-eosin histological, immunohistochemical, and ultrastructural studies confirmed the mesothelial phenotype of this tumor. To our knowledge, this is the first description of a lymph node adenomatoid tumor.


Cystic adenomatoid tumor of the mediastinum.

Plaza JA, Dominguez F, Suster S.

Department of Pathology, Division of Anatomic Pathology, Ohio State University, Columbus, Ohio; and dagger East Coast Pathology Associates, Melbourne, Florida.
Am J Surg Pathol. 2004 Jan; 28(1): 132-8. Abstract quote  

SUMMARY: A case of adenomatoid tumor presenting as a mass in the anterior mediastinum is described. The patient was a 56-year-old woman with left side chest wall pain who showed a mediastinal mass on chest x-ray and CT scans. Thorough clinical and radiographic examination did not reveal any evidence of tumor elsewhere. At surgery, the tumor was found adjacent to the anterior pericardial reflection. Grossly, the tumor measured 5.5 x 5.5 x 3 cm and showed a homogeneous cut surface with numerous cystic structures that varied from 0.5 to 1.5 cm in greatest diameter.

Histologic examination showed numerous cystic spaces lined by flattened or cuboidal epithelial cells. The walls of the cysts showed a proliferation of small canalicular structures lined by round to polygonal epithelioid cells with vacuolated eosinophilic cytoplasm. Immunohistochemical studies showed strong positivity of the epithelioid cells for AE1/AE3 cytokeratin, CK5/CK6, and calretinin. Stains for CK7, CK20, alpha-fetoprotein, CD31, carcinoembryonic antigen, MOC 31, and chromogranin were negative. Electron microscopic examination showed numerous long microvilli on the cell surface and abundant tonofilaments/desmosomal plaques in the tumor cells, characteristic of mesothelial cells.

The patient is alive and well and free of recurrence 1 year following surgery. Adenomatoid tumor is a rare neoplasm that should be added in the differential diagnosis of anterior mediastinal masses. Immunohistochemical and ultrastructural studies may be of aid in identifying the characteristic features of mesothelial cells and to avoid mistaking this lesion for more ominous conditions.

Adenomatoid tumor of the pancreas: a case report with comparison of histology and aspiration cytology.

Overstreet K, Wixom C, Shabaik A, Bouvet M, Herndier B.

Department of Pathology, University of California, San Diego Medical Center, San Diego, California 92103, USA.
Mod Pathol. 2003 Jun;16(6):613-7 Abstract quote  

We present a 58-year-old woman who presented with a 1.5-cm, hypodense lesion in the head of the pancreas. Endoscopic ultrasound-guided fine-needle aspiration yielded bland, monotonous cells with wispy cytoplasm, slightly granular chromatin, and small nucleoli.

A presumptive diagnosis of a neuroendocrine lesion was rendered. Whipple procedure yielded a well-circumscribed, encapsulated lesion with dense, hyalinized stroma and a peripheral rim of lymphocytes. Spindled and epithelioid cells formed short tubules, cords, and nests. The neoplasm stained for CK 5/6, calretinin, vimentin, CD 99, pancytokeratin, and EMA, consistent with mesothelial origin. This characteristic histology and immunohistochemistry is consistent with an adenomatoid tumor.

We believe we are the first to report this benign neoplasm in such an unusual location. Herein we address the diagnosis of adenomatoid tumor by histology, immunohistochemistry, and aspiration cytology. Our case is particularly unique in that the histology and cytology are compared and correlated.

Adenomatoid tumors of testis and epididymis: a report of two cases.

Gokce G, Kilicarslan H, Ayan S, Yildiz E, Kaya K, Gultekin EY.

Department of Urology and Pathology, Faculty of Medicine, Cumhuriyet University, Sivas, Turkey.
Int Urol Nephrol. 2001;32(4):677-80 Abstract quote  

Adenomatoid tumors are rare benign tumors of female and male genital tracts.

In this paper, we reported an epididymal and a testicular adenomatoid tumor in two patients presented with enlarged intrascrotal mass.


Adenomatoid tumors of the uterus: an analysis of 60 cases.

Nogales FF, Isaac MA, Hardisson D, Bosincu L, Palacios J, Ordi J, Mendoza E, Manzarbeitia F, Olivera H, O'Valle F, Krasevic M, Marquez M.

Department of Pathology, University Hospital, Granada, Spain.
Int J Gynecol Pathol. 2002 Jan;21(1):34-40. Abstract quote  

Sixty cases of uterine adenomatoid tumors (ATs) are reported. All except four were incidental findings in hysterectomy specimens, three of these being discovered preoperatively as large multicystic tumors. ATs were classified into two distinctive macroscopic patterns: small, solid tumors and large, cystic ones. The 56 small, solid ATs ranged from 0.2 to 3.5 cm, (average 2.1 cm); 48 were nodular and 8 diffuse. The four large, cystic tumors ranged from 7 to 10 cm. Inflammation occurred in 65% of the tumors, and a smooth muscle reaction, identified by an increased Ki-67 index, was present in most cases.

Both types were histologically similar except for the presence of short papillae in cystic tumors, which also showed serosal involvement. Both were immunoreactive for cytokeratins, calretinin, HMBE-1, and vimentin. Estrogen and progesterone nuclear receptors and EMA were negative. These tumors represent a spectrum ranging from small and solid to large and cystic ATs in the female genital tract, whereas outside the genital tract they are morphologically similar to multicystic mesothelioma.

Although a reactive origin for ATs often seems plausible, especially when inflammation is present, their neoplastic nature should not be ignored.



Thread-like bridging strands: A morphologic feature present in all adenomatoid tumors.

Hes O, Perez-Montiel DM, Alvarado Cabrero I, Zamecnik M, Podhola M, Sulc M, Hora M, Mukensnabl P, Zalud R, Ondic O, Michal M.

Ann Diagn Pathol. 2003 Oct;7(5):273-7 Abstract quote.  

Adenomatoid tumor (AT) is a benign, relatively rare neoplasm occurring primarily in the genital tract of both genders.

Histologically, ATs were composed of fibrous tissue, which are separated by numerous slit-like and pseudotubular spaces. Peculiar "thread-like bridging strands" (TBS) crossing the pseudotubular spaces are typical morphologic feature. In this study, the frequency of occurrence of these TBS within a large series of ATs in various organs was examined. Sixty-nine cases were included in our study.

Twenty-eight cases occurred in women, 41 cases in men. Tumors were located in the myometrium, fallopian tube, ovary, epididymis, tunica albuginea, and testicular parenchyma. Tumor size ranged from 0.8 to 8.2 cm (mean, 2.7 cm). TBS were found in 100% of cases. Presence of thin intraluminal TBS within ATs was a constant morphologic feature independently on gender and localization of the lesions.

Ultrastructurally, they were always formed by apposition of attenuated cytoplasm of two adjacent mesothelial cells.

In our opinion, TBS are morphologically very specific for ATs and we are not aware of any other epithelial structure in any organ demonstrating as appearance similar to these TBS of ATs.


Diffuse uterine adenomatoid tumor in an immunosuppressed renal transplant recipient.

Cheng CL, Wee A.

Department of Pathology, National University Hospital, Singapore, Republic of Singapore.
Int J Gynecol Pathol. 2003 Apr;22(2):198-201. Abstract quote  

A case of diffuse adenomatoid tumor of the uterus in an immunosuppressed renal transplant recipient is reported and compared with two previously reported, similar cases. The multinodular uterine lesion grossly resembled intramural leiomyomata except for a mucoid cut surface and a cystic serosal component.

The predominant patterns of the tumor were adenoid and angiomatoid with less prominent solid and cystic patterns. Immunohistochemical and ultrastructural studies confirmed the mesothelial nature of the tumor cells. Additionally, there was strong diffuse immunoreactivity for proliferating cell nuclear antigen, a low expression of Ki-67, and weak nuclear p53 staining.

The relationship between immunosuppression and diffuse adenomatoid tumors is discussed.

Uterine diffuse adenomatoid tumor. Does it represent a different biological entity?

Di Stefano D, Faticanti Scucchi L, Covello R, Martinazzoli A, Meli C, Bosman C.

Department of Experimental Medicine and Pathology, University La Sapienza, Rome, Italy.

Gynecol Obstet Invest. 1998;46(1):68-72. Abstract quote  

Adenomatoid tumor represents a type of mesothelioma apparently confined to the genital tract and characterized by its benign behavior. Its morphological aspects are well known and, until now, it has been described as a nodular mass except for a case diffusely infiltrating the entire myometrium in an immunosuppressed patient.

We report a case of benign mesothelial tumor characterized by histological, immunophenotypical and ultrastructural features of an otherwise typical adenomatoid tumor but diffusely growing below uterine serosal surface into the myometrium without discernible borders.

The existence of a diffuse type of adenomatoid tumor might reflect a different nature of this neoplasm leading to the hypothesis that this variant of benign mesothelioma represents a distinct biological entity.


Infarcted Adenomatoid Tumor: A Report of Five Cases of a Facet of a Benign Neoplasm That May Cause Diagnostic Difficulty.

Skinnider BF, Young RH.

Departments of Pathology and Laboratory Medicine, Vancouver Hospital and Health Sciences Center, and University of British Columbia, Vancouver, British Columbia, Canada; and the dagger James Homer Wright Pathology Laboratories of the Massachusetts General Hospital and the Department of Pathology, Harvard Medical School, Boston, Massachusetts.
Am J Surg Pathol. 2004 Jan; 28(1): 77-83. Abstract quote  

SUMMARY: We describe five cases in which adenomatoid tumors showed extensive necrosis, presumably due to infarction, and posed diagnostic difficulty. The tumors occurred in four males (three with epididymal tumors and one with an intratesticular tumor) and one female (with a parafallopian tube tumor) 35 to 44 years of age. Two of the men presented with acute scrotal pain simulating epididymitis, and two with a palpable mass. The parafallopian tube tumor was an incidental finding. The tumors were solitary, grossly well-circumscribed, uniformly solid masses that ranged in size from 1.1 to 3.5 cm.

Microscopically, they were all characterized by central necrosis with pale mummified adenomatoid tumor identified at least focally but often overshadowed by nondescript necrotic tissue. Viable adenomatoid tumor was identified in all cases but was minor in amount in two of them. The necrosis was surrounded by a florid reactive process of fibroblasts and myofibroblasts that had plump nuclei often with prominent nucleoli, and occasional mitoses. Two of the epididymal cases had adjacent rete testis showing epithelial hyperplasia with hyaline globule formation.

The microscopic appearance often suggested the possibility of a malignant neoplasm because of: 1) blurring of the normal relatively easily identifiable junction between adenomatoid tumor and adjacent tissue; 2) irregular pseudo-infiltration of fat by reactive tissue and adenomatoid tumor; 3) paucity of typical adenomatoid tumor due to the infarction and the fact that viable tumor usually showed a solid pattern; and 4) atypia of the associated reactive cells. This unemphasized feature of adenomatoid tumors may potentially lead to more aggressive therapy than warranted if it is not correctly interpreted.



Uterine adenomatoid tumors confirmed by immunohistochemical staining.

Irikoma M, Takahashi K, Kurioka H, Miyazaki K, Kamei T.

Department of Obstetrics and Gynecology, Shimane Medical University, Japan.
Arch Gynecol Obstet. 2001 Aug;265(3):151-4. Abstract quote  

We present a 39-year-old nulliparous woman who consulted our clinic for an 8-year history of infertility with no notable symptoms. There apparent uterine leiomyomas were found incidentally on clinical examination and imaging. The surgically enucleated specimens were white in color with variable consistency poorly defined margins.

The tissues stained positive for cytokeratin but were negative for CD34 antibodies, indicating a mesothelial origin. Staining for vimentin and HBME1 was also strongly positive, supporting a mesothelial origin of the tumors. The patient became pregnant 6 months after surgery.

A healthy male infant was delivered at term. Immunohistochemical staining establish the diagnosis of benign adenomatoid tumors derived from mesothelial tissue.

Immunohistochemical evidence for mesothelial origin of paratesticular adenomatoid tumour.

Delahunt B, Eble JN, King D, Bethwaite PB, Nacey JN, Thornton A.

Departments of Pathology, Wellington School of Medicine, University of Otago, New Zealand.
Histopathology. 2000 Feb;36(2):109-15 Abstract quote.  

AIMS: To investigate the histogenesis of paratesticular adenomatoid tumour by use of immunohistochemical markers for a variety of carcinomas and mesothelioma.

METHODS AND RESULTS: Immunohistochemical staining of sections from 12 cases of paratesticular adenomatoid tumour was undertaken using primary antibodies to antigens expressed by benign epithelial cells and carcinoma (cytokeratin AE1/AE3, cytokeratin 34ssE12, epithelial membrane antigen, MOC-31, Ber-EP4, CEA, B72.3, LEA.135, Leu M1), stromal and vascular markers (vimentin, CD34, factor VIII), and mesothelioma-associated antigens (thrombomodulin, HBME-1, OC 125) and p53 protein. There was absence of immunohistochemical expression of epithelial/carcinoma markers MOC-31, Ber-EP4, CEA, B72.3, LEA.135, Leu M1 and to factor VIII and CD34. All tumours expressed cytokeratin AE1/AE3, epithelial membrane antigen and vimentin, with weak expression of cytokeratin 34ssE12 in 25% of tumours. Each tumour showed expression of thrombomodulin, HBME-1 and OC 125 in a membranous distribution. p53 protein expression was not detected.

CONCLUSIONS: The immunohistochemical profile of paratesticular adenomatoid tumour is strongly supportive of a mesothelial cell origin.



Chronic epididymitis (epididymal nodule) mimicking an adenomatoid tumor--case report with review of literature.

Singh I, Dev G, Singh N.

Dept of Surgery, University College of Medical Sciences (University of Delhi) & Guru Tegh. Bahadur Hospital, Delhi-95, India.
Int Urol Nephrol. 2002;34(2):219-22 Abstract quote.

AIM: To describe and review the differential diagnosis of epididymal nodules and chronic epididymitis so as to have a broad view of this pathology. We have suggested a possible diagnostic algorithm for the workup of an epididymal nodule.

METHODS/RESULTS: We have reported a case of a 35-year-old patient with a symptomatic palpable nodular mass in the tail of the left epididymis. Fine needle aspiration suggested an adenomatoid tumor while the surgical excision histology was reported as chronic epididymitis.

CONCLUSIONS: Epididymal nodules are frequently encountered in the epididymis. Their differential diagnosis includes chronic granulomatous epididymitis, adenomatoid tumor and benign paratesticular neoplasms.

We consider that it is important to distinguish epididymal nodules from benign inflammatory lesions and the threshold for a surgical excision should be low as it is therapeutic and provides a definite diagnosis. Whilst the FNAC alone may not be always adequate to confirm diagnosis, an epididymectomy may be curative as well as diagnostic in selected cases.




SURGERY Complete removal

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