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LETTER TO EDITOR  
Year : 2011  |  Volume : 54  |  Issue : 4  |  Page : 856-858
Inflammatory myofibroblastic tumor of renal pelvis : A rare entity


Department of Pathology, T N Medical College and B Y L Nair Hospital, Mumbai, India

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Date of Web Publication6-Jan-2012
 

How to cite this article:
Shah VB, Anchinmane VT, Savant D. Inflammatory myofibroblastic tumor of renal pelvis : A rare entity. Indian J Pathol Microbiol 2011;54:856-8

How to cite this URL:
Shah VB, Anchinmane VT, Savant D. Inflammatory myofibroblastic tumor of renal pelvis : A rare entity. Indian J Pathol Microbiol [serial online] 2011 [cited 2019 Aug 24];54:856-8. Available from: http://www.ijpmonline.org/text.asp?2011/54/4/856/91533


Sir,

Inflammatory myofibroblastic tumor (IMFT) is a rare entity composed of spindle cells admixed with variable amounts of extracellular collagen, lymphocytes, and plasma cells. Despite many studies, IMFT remains a curious lesion. It was originally described in the lung and called plasma cell granuloma, [1] and now inflammatory myofibroblastic tumor is known to arise in a wide variety of body sites including abdominal cavity, retroperitoneum, bladder. [2],[3] In the genitourinary tract, the urinary bladder is the common site of occurrence. [2]

We report a rare case of IMFT of renal pelvis which clinically and radiologically mimicked malignancy.

A 42-year-old female presented with right flank pain and hematuria since five months. Computerized tomography revealed a polypoid tumor of 6 × 5 × 4 cm in the right renal pelvis suggestive of neoplastic etiology. Nephrectomy was performed.

Gross morphology showed a small hydronephrotic right kidney with thin atrophic cortex. The pelvis was markedly dilated and revealed a polypoidal mass of 6 × 5 cm with pelvicalyceal mucosal epithelium was smooth. The mass was firm and had a homogeneous translucent appearance on cut surface [Figure 1]b.
Figure 1: (a) Gross of right nephrectomy specimen showing a small hydronephrotic kidney with polypoidal mass occupying the dilated pelvis. (b) The cut surface of mass is homogenous with firm grey white appearance. (c) The small kidney with atrophic thin cortex

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Histopathology of the mass showed a cellular tumor with admixture of myofibroblasts and fibroblasts arranged in fascicles in a scant collagenous stroma with a polymorphic inflammatory cell component of lymphocytes and plasma cells in the background [Figure 2]a and b. Majority of the myofibroblastic cells showed bizarre hyperchromatic nucleus [Figure 2]c. However, mitoses and necrosis were absent in the tumor.
Figure 2: (a) Histopathology of the mass showing cellular tumor with admixture of myofibroblasts and fibroblasts arranged in fascicles. [Hematoxylin and Eosin stain, ´100] High power highlights the polymorphic inflammatory cell component composed of lymphocytes and plasma cells in the background seen in (b) and spindle tumor cells with bizarre hyperchromatic nucleus as seen in (c). [Hematoxylin and Eosin stain, ×400]

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The immunohistochemical stains revealed tumor cells positive for vimentin and smooth muscle actin [Figure 3]b. The tumor cells were negative for epithelial membrane antigen EMA, cytokeratin and desmin, HMB 45, S100. The lesion was diagnosed as inflammatory myofibroblastic tumor of renal pelvis.
Figure 3: Immunohistochemical stains: (b) Spindle tumor cells showing positivity for smooth muscle actin (SMA) and negative for alkaline lymphoma kinase (ALK1) seen in (c). Compare the spindle cells on Hematoxyline and Eosin stained section in (a). [Hematoxylin and Eosin stain, ×400]

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Inflammatory myofibroblastic tumor or inflammatory pseudotumor is a rare entity in the genitourinary tract with most cases occurring in the bladder. [2],[3] The first case report of IMFT of the renal pelvis was published in 1972, [4] and the kidney in 1976. [5] The morphologic criteria suggestive of IMFT include a variety cellular spindle cell tumor composed of reactive myofibroblasts with elongated nuclei admixed with variable amounts of a lymphoplasmacytic infiltrate.

These features are not totally specific to IMFT and may be seen in benign and malignant spindle cell tumor of renal pelvis. The clinical and radiological similarity of renal pelvis IMFT to sarcoma and urothelial carcinomas, spindle cell sarcoma may cause potential diagnostic problem. The negative stain for EMA and cytokeratin in the tumor cells ruled out the diagnosis of urothelial carcinoma. The gross morphology of polypoidal lesion, a fibroepithelial polyp should be excluded. The latter is usually composed of loose edematous and vascular stroma with fewer inflammatory cells covered by normal urothelium. Clinical presentation, careful histological examination and immunohistochemical studies will generally determine the appropriate diagnosis.

Features that help distinguish IMFTs from malignancies such as sarcomas include minimal nuclear atypia, normal mitotic figures not exceeding 5 per 10 high-power fields, the presence of an intense inflammatory cell infiltrate, granulation tissue, prominent small vessel networks, and the absence of necrosis. Immunohistochemical studies including our case support, the myofibroblastic nature of this lesion with expression of vimentin and smooth muscle actin.

The pathogenesis of IMFT remains uncertain, although initially the tumors were thought to represent a reactive inflammatory process or "pseudotumor". The controversial pathogenesis is reflected in the various terms that have been assigned to this entity, including plasma cell granuloma, inflammatory pseudotumor, pseudosarcomatous fibromyxoid tumor, and inflammatory myofibroblastic tumor.

Alkaline lymphoma kinase (ALK) 1 protein using immunohistochemical methods have shown positive staining in vesical IMFT (33-75%). [6] Our case was negative for ALK 1 by immunohistochemistry [Figure 3]c. A recent article by Kapusta et al. [7] a series of 12 IMFTs of renal and renal pelvis was studied and ALK 1 staining was done on all the cases. All the 12 cases of IMFT of kidney were negative for ALK 1, as also observed in our case. ALK1 negative IMFT of kidney may represent a subset of IMFT with different disease process or subset that may be reactive in nature.

The favorable outcome of most of these lesions, particularly in the lung and bladder is well known and has implications for initial surgical resection and follow-up. The neoplastic nature of renal IMFT remains uncertain. In the literature review of renal IMFTs, surgical excision has been the course of therapy with no evidence of recurrence or metastatic disease reported. [7] Complete surgical excision seems to be the best approach to management of primary inflammatory myofibroblastic tumors of renal pelvis.

Inflammatory pseudotumor of renal pelvis, despite being a rare tumor should be considered in the differential diagnosis of solitary renal pelvis tumor. The benign nature of this tumor warrants conservative surgical management. The absence of ALK1 in our case correlates with all the IMFTs of kidney reported in literature with typical histological features, thus providing additional support to the existing cases. Further study may, in time, better define the nature of this neoplasm and the optimal treatment approach.

 
   References Top

1.Umiker WO, Iversion L. Postinflammatory 'tumour' of of the lung. Report of four cases simulating xanthoma, fibroma or plasma cell granuloma. J Thorac Cardiovasc Surg 1954;28:55-63.  Back to cited text no. 1
    
2.Jones EC, Clement PB, Young RH. Inflammatory pseudotumour of the bladder: A clinicopathological immunohistochemical, ultrastructural and flow cytometric study of 13 cases. Am J Surg pathol 1993;17:264-74.  Back to cited text no. 2
[PUBMED]    
3.Coffin CM, Humphrey PA, Dehner LP. Extrapulmonary myofibroblastic tumour: A clinical and pathologic survey. Semin Diagn Pathol 1998;15:85-101.  Back to cited text no. 3
[PUBMED]    
4.Davidies KC, Johnson SH, Marshall JR. Plasma cell granuloma of the renal pelvis. J Urol 1972;107:938-9.  Back to cited text no. 4
    
5.Fisch AE, Brodey PA. Plasma cell granuloma of the kidney. Urology 1976;8:91.  Back to cited text no. 5
    
6.Freeman A, Greddes N, Munson P, Joseph J, Ramani P, Sandison A, et al. Anaplastic lymphoma kinase (ALK) staining and molecular analysis in inflammatory myofibroblastic tumours of the bladder a preliminary clinical pathological study of 9 cases and review of literature. Modern Pathol 2004;17:765-771.  Back to cited text no. 6
    
7.Kapusta LR, Weiss MA, Ramsay J, Lopez-Beltran A, Srigley JR. Inflammatory myofibroblastic tumors of the kidney: A clinicopathologic and immunohistochemical study of 12 cases. Am J Surg Pathol 2003;27:658-66.  Back to cited text no. 7
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Correspondence Address:
Vinaya B Shah
Department of Pathology, Flat No. 38, Building No. 2, K K Marg, Govt. Colony, Next to Race Course, Haji Ali, Mumbai - 400 034
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.91533

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