|Year : 2015 | Volume
| Issue : 3 | Page : 668
Inflammatory pseudotumor of kidney masquerading as renal carcinoma
Prakash Babu1, MK Kalpana Kumari2, HK Nagaraj1, Vijaya V Mysorekar2
1 Department of Urology, M. S. Ramaiah Medical College and Teaching Hospital, Bengaluru, Karnataka, India
2 Department of Pathology, M. S. Ramaiah Medical College and Teaching Hospital, Bengaluru, Karnataka, India
|Date of Web Publication||9-Oct-2015|
M K Kalpana Kumari
C 710, Sterling Residency, Dollars Colony, Bengaluru - 560 094, Karnataka
Source of Support: None, Conflict of Interest: None
Inflammatory pseudotumor also known as inflammatory fibroblastic tumor is a rare benign tumor, which commonly affects the lung. It is very rarely seen in the genitourinary tract. As the preoperative diagnosis, clinically and radiologically is inconclusive, it is imperative to surgically remove and confirm it on histopathologic examination. We report a case of inflammatory pseudotumor in a 51-year-old male who presented with flank pain and was treated with nephrectomy.
Keywords: Granuloma, inflammatory myofibroblastic tumor, inflammatory pseudotumor
|How to cite this article:|
Babu P, Kalpana Kumari M K, Nagaraj H K, Mysorekar VV. Inflammatory pseudotumor of kidney masquerading as renal carcinoma. J Can Res Ther 2015;11:668
| > Introduction|| |
Inflammatory pseudotumor is a rare benign tumor of unknown causes. There are <20 cases of inflammatory pseudotumor of kidney reported in English literature.  Several alternative names have been used for inflammatory pseudotumor such as inflammatory myofibroblastic tumor (IMT), plasma cell granuloma, xanthomatous pseudotumor, pseudosarcomatous myofibroblastic proliferation and myofibroblastoma.  The WHO classifies inflammatory pseudotumor as a distinct borderline lesion and recent studies have revealed its neoplastic nature with clonal abnormality and anaplastic lymphoma kinase expression.  It generally affects the lung and orbit and rarely urogenital tract. It was first described in the urogenital tract in the renal pelvis by Davides in 1972 and has been identified in the urethra and bladder, which is the most common site in the genitourinary tract and the kidney has been a very rare site. 
| > Case report|| |
A 51-year-old male patient presented with the complaints of the left flank pain since 1 month. There was no history of hematuria. General physical and urological examinations were unremarkable. Urine microscopy was within normal limits. Abdominal ultrasonography revealed left contracted kidney with cortical calcification and mild hydronephrosis. Contrast-enhanced computed tomography (CECT) [Figure 1] of abdominopelvic region demonstrated a mass 8.2 cm × 4.4 cm × 4.6 cm, involving the upper and mid pole of the left kidney extending medially and encasing the left renal artery up to the left lateral wall of aorta and extending along the left ureter with slight enhancement, which was suggestive of tuberculosis or a malignant tumor (renal cell carcinoma or transitional cell carcinoma). However, the evaluation for tuberculosis was negative. The patient was subjected to CT guided biopsy, which was reported as chronic pyelonephritis. A laparoscopic left radical nephrectomy was performed with a diagnosis of renal cell carcinoma. The intraoperative findings correlated with the CT finding. The patient remained pain free during outpatient clinic follow-up. Grossly the left kidney showed an irregular, invasive grey white growth [Figure 2] and microscopy revealed benign tumor comprising of numerous interlacing fascicles of benign spindle cells, infiltrated by dense inflammatory cells comprised of plasma cells, eosinophils and lymphocytes. There were many collagen bundles amidst which was seen focal xanthogranulomatous change [Figure 3]. Immunohistochemical studies demonstrated strong positivity for vimentin, smooth muscle actin (SMA), but focal positivity for anaplastic lymphoma kinase (ALK) [Figure 4],[Figure 5] and [Figure 6].
|Figure 1: Computed tomography scan showing a hypodense mass involving the left kidney with slight contrast-enhancement|
Click here to view
|Figure 2: Cut section of left kidney showing an irregular, invasive grey white growth|
Click here to view
|Figure 3: Photomicrograph (H and E, ×400), fascicles of spindle cells with areas of hyalinized collagen bundles infiltrated by numerous plasma cells|
Click here to view
| > Discussion|| |
Inflammatory pseudotumor or IMT is a spindle cell proliferation with a distinctive fibroinflammatory and pseudosarcomatous appearance. Coffin et al.  have shared their experience with 84 cases occurring in the soft tissues and viscera. Patients usually present with hematuria and abdominal pain. In our case, the patient came with complaints of flank pain due to which he was provisionally diagnosed to have calculous pyelonephritis.
Cases have been reported in patients between ages of 3 and 68 years, most of them males,  in our case it was a 51-year-old male patient.
Even though, the literature states that clinical examination and radiological investigations are inconclusive and diagnosis is made at the time of surgical intervention, Park et al.  have described the imaging features of inflammatory pseudotumor of the genitourinary tract and observed that inflammatory tumor of the kidney can be seen as hypo or heterogeneous echoic mass on sonography, well-defined hypoechoic mass with intramural vascularity on enhanced power Doppler sonography, low attenuation mass on CT and hypovascular lesion on magnetic resonance imaging. It is very difficult to differentiate inflammatory pseudotumor from a malignant lesion, and definite radiologic differentiation from malignancy is not possible. However, familiarity with the radiological manifestations of inflammatory pseudotumor can avoid unnecessary surgery. In our case, CECT had suggested a malignant tumor, renal cell carcinoma or transitional cell carcinoma or tuberculous pyelonephritis.
Histological examination is very important to identify inflammatory pseudotumor as a benign tumor rather than a reactive process. Inflammatory pseudotumor consists of proliferation of spindle cells admixed with various amounts of lymphocytic infiltrate.  Coffin et al.  have demonstrated positivity for vimentin, muscle specific actin and cytokeratin coexistent in myofibroblasts of extrapulmonary inflammatory pseudotumor. In our case also the tumor cells showed strong positivity for vimentin and SMA. In cases with more compact arrangement of spindle cells with atypical cells the differential diagnosis of sarcomatoid carcinoma, and in cases with extensive inflammation conditions such as inflammatory leiomyosarcoma, inflammatory fibrosarcoma, and where IMT is rich in histiocytes, malignant histiocytofibroma, should be considered. 
The pathogenesis of inflammatory pseudotumour remains uncertain. Initially, it was thought to represent a reactive inflammatory process, hence the name pseudotumor. The inflammatory reaction could be secondary to surgery, trauma or infection. No single etiology or pathogenesis has been established for inflammatory pseudotumor. Some cases may be related to infections such as actinomyces, pseudomonas and mycoplasma. Another etiologic agent is Epstein-Barr virus.  Alternatively, there have been postulations that it has an autoimmune origin given its association with various autoimmune diseases. 
On the contrary, others consider that inflammatory pseudotumor is a neoplastic process with low malignant potential which can be locally aggressive and rarely metastasizes. 
Recurrences were reported in association with an, abdominopelvic site, a larger size and an older age. Metastasis however were associated with younger age, larger size, abdominal and pulmonary sites. 
Recurrences of inflammatory pseudotumor in the genitourinary tract have not been reported in the literature. Comparing the clinicopathologic and histologic features and ALK expression in inflammatory pseudotumor, Coffin et al.  concluded that ALK reactivity is a favorable prognostic indicator and abdominopelvic inflammatory pseudotumor recurs more frequently. In our case the spindle cells were focally positive for ALK.
Inflammatory pseudotumors express ALK protein which is triggered by ALK gene at 2p23, IMT-rearrangement (IMT-RA), which is seen in 36-60% of cases and are associated with aggressive clinical course. The IMT-RA can be detected by fluorescence in situ hybridization and reverse transcriptase-polymerase chain reaction. IMT-RA cases should be treated with surgical resection and chemotherapy with ALK inhibitor. 
For patients who are unable to undergo complete resections, multiple lesions or disease in an area, which are unrespectable, other modalities have been suggested. Corticosteroid monotherapy and nonsteroidal anti-inflammatory agents may be extremely efficacious. Radiation alone may induce enduring remission. Anecdotal response to chemotherapy has also been reported. 
| > Conclusion|| |
Although renal inflammatory pseudotumor is a very rare tumor with a favorable outcome, awareness of its existence in the differential diagnosis of a renal mass is critical to avoid misdiagnosis. Clinical presentation, careful histopathological examination and immunohistochemical studies will determine the accurate diagnosis.
| > References|| |
Khallouk A, Ahallal Y, Tazi MF, Elfatemi H, Tazi E, Elammari J, et al
. Inflammatory pseudotumor of the kidney: A case report. J Med Case Rep 2011;5:411.
Park SB, Cho KS, Kim JK, Lee JH, Jeong AK, Kwon WJ, et al
. Inflammatory pseudotumor (myoblastic tumor) of the genitourinary tract. AJR Am J Roentgenol 2008;191:1255-62.
Lee NG, Alexander MP, Huihong Xu, Wan DS. Renal inflammatory myofibroblastic tumor: A case report and comprehensive review of literature. World J Oncol 2011;2:85-8.
Coffin CM, Watterson J, Priest JR, Dehner LP. Extrapulmonary inflammatory myofibroblastic tumor (inflammatory pseudotumor). A clinicopathologic and immunohistochemical study of 84 cases. Am J Surg Pathol 1995;19:859-72.
Elfatemi H, Laila C, Znati K, Tazi MF, Ahallal Y, Tazi E, et al
. Anaplasic lymphoma kinase positive inflammatory myofibroblastic tumour with renal pelvic calculus: A case report. Cases J 2009;2:6373.
Ryu KH, Im CM, Kim MK, Kwon D, Park K, Ryu SB, et al
. Inflammatory myofibroblastic tumor of the kidney misdiagnosed as renal cell carcinoma. J Korean Med Sci 2010;25:330-2.
Chen CY, Liou JH, Liao YM. Inflammatory myofibroblastic tumor of the kidney associated with a renal stone. Journal of Taiwan urological association 2008;19:235-8.
Coffin CM, Hornick JL, Fletcher CD. Inflammatory myofibroblastic tumor: Comparison of clinicopathologic, histologic, and immunohistochemical features including ALK expression in atypical and aggressive cases. Am J Surg Pathol 2007;31:509-20.
Li J, Yin WH, Takeuchi K, Guan H, Huang YH, Chan JK. Inflammatory myofibroblastic tumor with RANBP2 and ALK gene rearrangement: A report of two cases and literature review. Diagn Pathol 2013;8:147.
Chavez C, Hoffman MA. Complete remission of ALK-negative plasma cell granuloma (inflammatory myofibroblastic tumor) of the lung induced by celecoxib: A case report and review of the literature. Oncol Lett 2013;5:1672-6.10.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]