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CytoJournal 2009,  6:7

Cytologic features of metanephric adenoma of the kidney

1 Department of Pathology, University Hospitals, Puerta de Hierro, Madrid, Spain
2 Department of Pathology, University Hospitals, La Paz, Madrid, Spain

Date of Submission19-Nov-2008
Date of Acceptance10-Dec-2008
Date of Web Publication04-Apr-2009

Correspondence Address:
Jose A Jimenez-Heffernan
Department of Pathology, University Hospitals, Puerta de Hierro, Madrid
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1742-6413.49164

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How to cite this article:
Jimenez-Heffernan JA, Tejerina E, Gonzalez-Peramato P, Vicandi B, Lopez-Garcia A. Cytologic features of metanephric adenoma of the kidney. CytoJournal 2009;6:7

How to cite this URL:
Jimenez-Heffernan JA, Tejerina E, Gonzalez-Peramato P, Vicandi B, Lopez-Garcia A. Cytologic features of metanephric adenoma of the kidney. CytoJournal [serial online] 2009 [cited 2019 Nov 14];6:7. Available from: http://www.cytojournal.com/text.asp?2009/6/1/7/49164

To the Editor,

Metanephric adenoma (MA) is a rare, benign renal neoplasm that consists of a proliferation of small epithelial cells, which form acinar, tubular, papillary and glomeruloid structures. The first large series describing the tumor were reported in 1995. [1,2] In many cases, the benign behavior, well-defined limits and small size of the tumors, make them candidates of conservative surgical management. That only a few cytological descriptions are available [3-9] is a reflection on the rarity of the tumor [Table 1]. We describe a case evaluated intraoperatively and in which cytology allowed a precise recognition.

A 56 - year-old woman, presented with a 3 cm renal tumor. Tumorectomy with intraoperative evaluation was performed. The renal mass was well defined, solid and had a grey to white color. Air-dried and alcohol-fixed cytologic samples were obtained after scraping the tumor surface. The smears showed a monomorphous cellular population in a clean background. Most cells presented as naked nuclei, with oval to round morphology. They distributed as clusters and single cells. A minimum amount of deeply stained cytoplasm was evident only in a few aggregates. Many clusters showed an evident tubular arrangement [Figure 1a]. Small, three-dimensional, tightly packed morules were present with a smooth outer surface [Figure 1b]. Ribbons, glandular [Figure 2a] and pseudo-papillary structures were also present. The nuclei were slightly oval and monomorphic [Figure 2b]. Chromatin was regularly distributed and the nuclear membrane was smooth; no nucleolus was seen. The smears showed no atypia, mitotic figures, necrosis or crushing chromatin artefact. Histology revealed an un-encapsulated neoplasm, with a predominant acinar and tubular growth, with pseudo-papillary and solid areas and inconspicuous stroma [Figure 3a] and [Figure 3b]. Glomeruloid structures were also seen. The cells were small, oval, and uniform with scanty cytoplasm. No nuclear atypia, mitotic figures or apoptosis were seen. Tumoral stroma was inconspicuous, with no necrosis. Immunohistochemistry revealed expression of vimentin, CD57 and WT1. There was no expression of cytokeratin 7 or epithelial membrane antigen.

In our opinion, the histopathologic features of MA are well reflected on cytology, allowing its recognition. The present case, as well as previously published ones, reveal a similar cytologic pattern that can be summarized as a small blue cell, epithelial tumor, with oval cells and no atypia. It shows different epithelial structures with tubules, glands, pseudopapillae and morules. In our case, the presence of numerous single cells is probably related to the scraping of the tumor, since fine needle aspirate samples show a marked predominance of clusters. [2, 3, 5-9] This cytologic image differs considerably from that of other adult renal tumors. The extensive use of image studies has resulted in the detection of many small renal masses.

Therapeutic decisions partially depend on the histologic nature of the tumor, but obtaining this information preoperatively may be difficult. Fine needle aspiration and intraoperative studies are often requested for aiding in decision making.

The present case illustrates the utility of cytologic evaluation of intraoperative tissue samples. Frozen sections raised the possibility of papillary renal cell carcinoma. This is an obvious consideration in the differential diagnosis of MA, since both neoplasms may share histologic features. [1,2] In our case, papillary renal cell carcinoma was not considered after cytologic evaluation. Instead, the small cell size and epithelial nature raised the possibilities of nephroblastoma and MA. Cellular monomorphism, absence of stromal component, extensive epithelial differentiation, oval morphology, absence of necrosis and apoptosis, as well as the patient's age, favored the possibility of MA. Epithelial-predominant nephroblastoma may resemble MA more closely. In fact, there are also immunohistochemical similarities, and, for some authors, MA represents a hyperdifferentiated, mature form of nephroblastoma. [10]

Papillary carcinoma and MA may share architectural features. Tubular, pseudo-papillary structures and spherules of tumoral cells can be present in both neoplasms. [1] However, the neoplastic cells differ. Those from papillary carcinoma are larger and show moderate amounts of cytoplasms, sometimes vacuolated or containing hemosiderin. The macrophagic cell population so frequently present in papillary carcinoma is rare in MA.

In conclusion, cytology, either as fine needle aspirates or during intraoperative procedures, may be of great value in the recognition of MA.[11]

 » Competing Interest Statement by all Authors Top

No competing interest to declare by any of the authors.

 » Authors' Contributions Top

JAJH, Conceptual organization, participated in the intraoperative diagnosis and writing of manuscript

ET, Participated in the intraoperative and histopathologic diagnosis and manuscript review

PGP and BV, Cytologic review of the case, differential diagnosis and manuscript review

AL, Conceptual organization, cyto-histologic evaluation and manuscript review

 » References Top

1.Jones EC, Pins M, Richard Dickersin G, Young RH. Metanephric adenoma of the kidney: A clinicopathological, immunohistochemical, flow cytometric, cytogenetic, and electron microscopic study of seven cases. Am J Surg Pathol 1995;19:615-26.  Back to cited text no. 1    
2.Davis CJ, Barton JH, Sesterhenn IA, Mostofi FK. Metanephric adenoma: Clinicopathological study of fifty patients. Am J Surg Pathol 1995;19:1101-14  Back to cited text no. 2    
3.Zafar N, Spencer D, Berry AD 3rd. Embryonal adenoma of the kidney: A report of two cases. Diagn Cytopathol 1997;16:42-6  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Renshaw AA, Maurici D, Fletcher JA. Cytologic and fluorescence in situ hybridization (FISH) examination of metanephric adenoma. Diagn Cytopathol 1997;16:107-11  Back to cited text no. 4  [PUBMED]  [FULLTEXT]
5.Granter SR, Fletcher JA, Renshaw AA. Cytologic and cytogenetic analysis of metanephric adenoma of the kidney: A report of two cases. Am J Clin Pathol 1997;108:544-9  Back to cited text no. 5  [PUBMED]  
6.Xu X, Acs G, Yu GH, Guttenberg M, Vautou RJ. Aspiration cytology of metanephric adenoma of the kidney. Diagn Cytopathol 2000;22:330-1  Back to cited text no. 6    
7.Khayyata S, Grignon DJ, Aulicino MR, Al-Abbadi MA. Metanephric adenoma vs Wilms' tumor: A report of 2 cases with diagnosis by fine needle aspiration and cytologic comparisons. Acta Cytol 2007;51:464-7  Back to cited text no. 7  [PUBMED]  
8.Bosco M, Galliano D, La Saponara F, Pacchioni D, Bussolati G. Cytologic features of metanephric adenoma of the kidney during pregnancy: A case report. Acta Cytol 2007;51:468-72  Back to cited text no. 8  [PUBMED]  
9.Portugal R, Barroca H. Clear cell sarcoma, cellular mesoblastic nephroma and metanephric adenoma: Cytological features and differential diagnosis with Wilms tumour. Cytopathology 2007;19:80-5.  Back to cited text no. 9  [PUBMED]  [FULLTEXT]
10.Argani P. Metanephric neoplasms: The hyper differentiated, benign end of the Wilms' tumor spectrum. Clin Lab Med 2005;25:379-92  Back to cited text no. 10  [PUBMED]  [FULLTEXT]
11.Granter SR, Perez-Atayde AR, Renshaw AA. Cytologic analysis of papillary renal cell carcinoma. Cancer 1998;84:303-8.  Back to cited text no. 11  [PUBMED]  [FULLTEXT]


  [Figure 1a], [Figure 1b], [Figure 2a], [Figure 2b], [Figure 3a], [Figure 3b]

  [Table 1]

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