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Year : 2021  |  Volume : 64  |  Issue : 2  |  Page : 343-346
Multilocular cystic renal oncocytoma—Awareness of an unusual morphologic variation


1 Department of Pathology, Shri Siddhivinayak Ganpati Cancer Hospital, Miraj, Maharashtra, India
2 Consultant Pathologist, Histopathology Department, Deep Pathology Laboratory, Miraj, Maharashtra, India

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Date of Submission06-May-2020
Date of Decision27-Jul-2020
Date of Acceptance12-Sep-2020
Date of Web Publication9-Apr-2021
 

   Abstract 


Background: Renal oncocytomas are benign epithelial tumors usually detected incidentally. They are typically solid,well-circumscribed,homogenous,mahoganybrown with a central stellate scar.Sometimes,they can have cystic degenerationand rarely present as a multilocular cyst which can be mistaken for other cystic renal carcinomas. Methods: We describe a case of incidentally detected multilocular cystic renal oncocytoma having an unusual gross appearance of multiloculation with perinephric fat invasion. The tumor exhibited tubulocystic architecture posed a diagnostic dilemma. Detailed study of multiple sections coupled with immunohisto chemistry helped elucidate the diagnosis. Till date, only eight cases of multicystic renal oncocytoma have been reported in the English literature. Conclusions: We emphasize the importance of awareness of this unusual morphologic variation to ensure correct diagnosis.

Keywords: Cystic, multilocular, oncocytoma, renal

How to cite this article:
Jagdale RV, Pol JN. Multilocular cystic renal oncocytoma—Awareness of an unusual morphologic variation. Indian J Pathol Microbiol 2021;64:343-6

How to cite this URL:
Jagdale RV, Pol JN. Multilocular cystic renal oncocytoma—Awareness of an unusual morphologic variation. Indian J Pathol Microbiol [serial online] 2021 [cited 2021 May 8];64:343-6. Available from: https://www.ijpmonline.org/text.asp?2021/64/2/343/313257





   Introduction Top


Renal oncocytoma (RO) is a benign renal epithelial neoplasm originating from the intercalated cells. It comprises 5–7% of all primary renal neoplasms and has an excellent prognosis. Typically RO is solid, well-circumscribed, homogenous, mahogany brown with a central stellate scar.[1],[2] RO is known to have several cytoarchitectural variations, hence can mimic several other renal neoplasms, although most ROs are solid, a few of them can show microscopic central cystic degeneration. However, macroscopic multiloculation is extremely rare. Only eight cases of multicystic renal oncocytoma (MRO) have been reported in the English literature. We report an unusual case of multilocular cystic RO, which posed a diagnostic challenge.


   Case Report Top


A 65-year male presented with bladder outlet obstruction (BOO) of 2 years duration and wished to get treated for his prostatic enlargement. He had no relevant medical history. His clinical examination revealed fullness in the left loin. Digital rectal examination showed moderate prostatomegaly. His laboratory investigations including Sr. PSA [Serum PSA] were within normal limits. Ultrasonography and CT scan of the abdomen revealed an incidental, large heterogeneous multilocular cystic mass in the lower pole of left kidney [Figure 1]a. It measured 8 × 7 cm with extrarenal spread. Cystoscopy showed moderate prostatomegaly and unremarkable urinary bladder. Left radical nephrectomy was performed.

Grossly, the kidney showed a fairly circumscribed, multilocular cystic tumor measuring 6.5 × 5.6 × 5.3 cm in the lower pole. Cut section was yellow-gray with few firm gritty areas and multiple micro- and macro-cysts filled with yellowish fluid and occasional cysts extending in the perinephric fat [Figure 1]b and [Figure 1]c. Microscopically, tumor showed dilated tubules and cysts lined by round to polygonal cells with abundant, eosinophilic granular cytoplasm and uniform round nuclei. Occasional nuclei showed prominent nucleoli. Few cells showed bi-nucleation. Occasional cells with hobnailing and floating incomplete septae were noted. Focal calcification was seen. Nuclear atypia, mitoses, and necrosis were absent. No clear or reticulated cells were noted. The tumor cysts invaded the perinephric fat. Vascular invasion was absent. This histopathology was suggestive of a multicystic RO [Figure 2] and [Figure 3]. However, a possibility of tubulocystic renal cell carcinoma (TRCC), multilocular cystic renal neoplasm of low malignant potential (MC-LMP), and low-grade renal cell carcinoma with oncocytic features needed an exclusion.

On immunohistochemistry (IHC), the tumor expressed panCK, PAX8, and CD117 and was immunonegative for EMA, CK7, CD10, AMACR, and vimentin [Figure 4]. Thus, the histomorphology and IHC results confirmed the diagnosis of multilocular cystic RO.
Figure 1: (a) CT abdomen shows a large complex multilocular cystic mass in the left kidney. (b and c) Nephrectomy specimen shows a multilocular cystic tumor with cysts extending in the perinephric fat

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Figure 2: H and E sections show (a and b) tubulocystic architecture (×40, ×100), (c) hobnailing and floating incomplete septation (×100), (d) typical solid nests of oncocytic cells in a hyalinized stroma (×100), (e) oncocytic cells with uniform round nuclei and occasional prominent nucleolus (×400), and (f) hyalinized fibrous scar and calcification (×40

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Figure 3: (a and b) Tumor cysts invading the perinephric fat (×100). (c and d) Sections from the solid area show tubules within the fibrotic and hyalinized stroma (×40, ×100)

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Figure 4: On IHC, tumor cells express (a) panCK, (g) PAX8, and (h) CD117 (inset ×400) and are immunonegative for (b) EMA, (c) vimentin, (d) CK7, (e) CD10, and (f) AMACR (×100)

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   Discussion Top


RO is a benign renal epithelial neoplasm constituting 5–7% of all primary renal epithelial tumors.[1],[2] Most ROs are asymptomatic and discovered incidentally during investigation of nonurologic problems. About 10% of patients present with hematuria, flank pain, or a palpable mass.[1] Our case was incidentally detected during evaluation for BOO.

These are slow growing with pushing borders that compress adjacent renal parenchyma and may give a gross impression of encapsulation.[1] They are typically solid, well-circumscribed, homogenous mahogany brown with a central stellate scar. The average size is 4–5 cm.[1],[2] Although most ROs are solid, a small proportion can show central cystic degeneration.[1] However, RO presenting as a multilocular cyst is extremely unusual and such cases are usually mistaken for renal cell carcinoma with a cystic component[3] or TRCC.[4] Ogden et al., in 1987, first described MRO.[5] Overall eight cases of MRO have been reported in the English literature, with one case report from India.[3],[6],[7],[8],[9],[10]

The differential diagnosis of multicystic renal neoplasms ranges from cystic nephroma, cystic RO, MC-LMP, and TRCC. Most of these tumors have an excellent prognosis. However, every attempt must be made to correctly diagnose MRO, as these are benign tumors.

MC-LMP is composed entirely of numerous cysts; the septae are lined by a single layer or groups of clear cells without expansile growth. The tumor cells express CK, EMA, CD10, vimentin, and CK7 and are negative for CD117 and AMACR. TRCC is well circumscribed with pure tubular and cystic architectural growth. The tubules and cysts are lined by flat, cuboidal cells with hobnailing, enlarged irregular nuclei with high nucleolar grade in fibrous stroma and lack solid islands. TRCC usually express vimentin, CK, CD10, AMACR, and CK7 and are immunonegative for CD117.

The presence of at least focal solid growth and islands of oncocytic tumor cells interspersed with loose stroma, lower nucleolar grade, absence of necrosis, and mitoses are strongly suggestive of MRO. Almost, all ROs express CD117 and panCK and are negative for CK7, CD10, and vimentin.[4]

A recently described fumarate hydratase-deficient renal cell carcinoma (FH-deficient RCC) can be one of the differentials, since they exhibit multiple morphologic patterns. These are seen in younger patients and demonstrate aggressive course. Most often they exhibit papillary architecture; sometimes they show tubulocystic pattern with low-grade morphology confusing with TRCC and MRO. Large eosinophilic viral-like macronucleoli at least focally, and a combined IHC testing for FH and 2SC, facilitates the detection of FH-deficient RCC.[11]

The histomorphology in our case showed a predominantly tubulocystic architecture with small-to-intermediate sized cysts lined by single layer of cuboidal cells with round uniform nuclei with occasional prominent nucleoli and abundant eosinophilic cytoplasm with loose stroma. The prominent oncocytic cells and the lack of clear lining cells almost ruled out MC-LMP. Some of the cells showed hobnailing and incomplete septations hanging free in the cyst lumina mimicking a TRCC. The tubules and cysts invaded the perinephric fat with minimal stromal response. Multiple additional sections showed an area of hyalinized stroma with typical solid nests of oncocytes pointing toward a diagnosis of RO. Expression of CD117 and negative AMACR, CD10, CK7, EMA, and vimentin aided in ruling out the differentials and confirming MRO. Our case showed two notable features—the presence of calcification within the hyalinized stroma and invasion of perinephric fat. Calcification in hypocellular stroma possibly represents dystrophic calcification in a long-standing tumor.[1] Perez-Ordonez et al. in their series of 70 cases of RO documented calcification in 31% cases and perinephric fat invasion in 20% of RO.[1] Leroy et al. reported perinephric fat extension in one of his cases of cystic RO and concluded to have no prognostic significance.[3] Thus, perinephric fat invasion probably has no influence on the benign nature of RO, well authenticated by the fact that our patient is fine since the last 9 years.

We present this case for its rarity and to create awareness about this unfamiliar morphologic variation of RO. The key feature to the diagnosis of multilocular cystic RO with such tubulocystic morphology is the demonstration of typical nests of oncocytes within the stellate scar by multiple sampling and taking the aid of IHC, as it is likely to be misdiagnosed for cystic renal carcinomas like MC-LMP or TRCC. We conclude that in a multilocular cystic renal neoplasm, one must focus on the epithelial cells lining cyst—clear or eosinophilic and their nuclear features, take multiple sections, be aware of the morphologic variations, run relevant IHC panel comprising of CK7, CD10, vimentin, AMACR, and CD117 to resolve the diagnostic dilemma.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Perez-Ordonez B, Hamed G, Campbell S, Erlandson RA, Russo P, Gaudin PB, et al. Renal oncocytoma: A clinicopathologic study of 70 cases. Am J Surg Pathol 1997;21:871-83.  Back to cited text no. 1
    
2.
Amin MB, Crotty TB, Tickoo SK, Farrow GM. Renal oncocytoma: A reappraisal of morphologic features with clinicopathologic findings in 80 cases. Am J Surg Pathol 1997;21:1-12.  Back to cited text no. 2
    
3.
Leroy X, Aubert S, Lemaitre L, Haffner J, Biserte J, Gosselin B. Multilocular cystic renal oncocytoma. J Clin Case Pathol 2006;59:223-4.  Back to cited text no. 3
    
4.
Skenderi F, Ulamec M, Vranic S, Bilalovic N, Peckova K, Rotterova P, et al. Cystic renal oncocytoma and tubulocystic renal cell carcinoma: Morphologic and immunohistochemical comparative study. Appl Immnohistochem Mol Morphol 2016;24:112-9.  Back to cited text no. 4
    
5.
Ogden BW, Beckman EN, Rodriguez FH Jr. Multicystic renal oncocytoma. Arch Pathol Lab Med 1987;111:485-6.  Back to cited text no. 5
    
6.
Schmidt PR, Bock D, Gasser G, Redtenbacher S. Multicystic renal oncocytoma. Urologe A 1991;30:253-5.  Back to cited text no. 6
    
7.
Shimoda J, Matsukawa H, Shimizu S, Kigure T, Harada T. A case of renal oncocytoma with multilocular cyst. Hinyokika Kiyo 1991;37:899-902.  Back to cited text no. 7
    
8.
Kodama K, Nagano K, Akimoto M, Suzuki S. Small renal oncocytoma with central cystic degeneration. Int J Urol 2004;11:110-3.  Back to cited text no. 8
    
9.
Syriac S, Mojica W, Chen F, Zhang S. Cystic renal oncocytoma: A case report with review of the literature. N A J Med Sci 2009;2:97-8.  Back to cited text no. 9
    
10.
Balaji AR, Prakash J, Darlington D. Cystic renal oncocytoma mimicking renal cell carcinoma. Urol Ann 2019;11:98-101.  Back to cited text no. 10
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11.
Trpkov K, Siadat F. Immunohistochemical screening for the diagnosis of succinate dehydrogenase-deficient renal cell carcinoma and fumarate hydratase-deficient renal cell carcinoma. Ann Transl Med 2019;7(suppl 8):S324.  Back to cited text no. 11
    

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Correspondence Address:
Rakhi V Jagdale
Department of Pathology, Shri Siddhivinayak Ganpati Cancer Hospital, Miraj, Sangli - 416 410, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/IJPM.IJPM_502_20

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

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