Inflammatory myofibroblastic bladder tumor: A very rare presentation

Inflammatory myofibroblastic tumor (IMT) is a rare benign lesion with similarities to malignant lesions due to possible aggressive behavior. Although highly uncommon, this condition usually occurs in lungs and retroperitoneum. The involvement of the genitourinary tract represents a singular occasion. May present with nonspecific manifestations such as painless hematuria, dysuria, voiding urgency and low abdominal pain. We describe a Case of a 55-year-old patient who presented to the urology service complaining of hematuria. Imaging studies showed a 62mm lesion on the upper right side of the bladder and the diagnosis of IMT was confirmed by immunohistochemical evaluation after laparoscopic partial cystectomy.


Introduction
Inflammatory myofibroblastic tumor (IMT) is a rare benign lesion that has similarities to malignant lesions due to possible aggressive behavior, although its specific potential for malignancy has not been determined. 1 It is a soft tissue tumor, which evolves through myofibroblastic differentiation and is characterized by the infiltration of inflammatory cells into the tissue. The etiology of its development remains uncertain, but there are studies that suggest possible occurrence secondary to infections, trauma or pelvic surgeries. 2,3

Case presentation
AC, 55 years old, woman, presented to the Urology Service complaining of hematuria. His previous medical history includes indolent lymphoma and hypothyroidism. During cystoscopy, a massive lesion was identified in the bladder fundus, right lateral wall, occupying 2/3 of the bladder lumen, with area of necrosis and 4cm pedicled component of length, with 8cm of average, it was confirmed with a Magnetic Resonance Imaging (MRI) of the pelvis (Fig. 1). Pathological study demonstrated spindle-cell proliferation without atypical in lamina propria, with abundant myxoid stroma (Fig. 2).
The patient had received blood transfusion at admission and after two weeks, when the serum hemoglobin levels were 4.9 g/dL, and in the preoperative period, when the levels were 7.3 g/dL. She underwent partial laparoscopic cystectomy with a combined approach (Fig. 3). Post-op evolution was good, with hospital discharge in the fifth day. Immunohistochemical analysis revealed positivity for smooth muscle actin (1A4), CK AE1/AE3, ALK, Desmina and Ki67, findings compatible with the diagnosis of inflammatory myofibroblastic tumor ( Fig. 1).

Discussion
Just over 100 cases of bladder IMT have been reported worldwide since 1980, when the syndrome was first described. 1 Thus, it is an uncommon lesion and without sufficient evidence in the literature that allows consensus in the diagnostic and therapeutic approach. When present, this condition usually occurs in the lungs and retroperitoneum, and tends to occur in younger populations. The involvement of the genitourinary tract represents an even more singular occasion, being apparently more prevalent, in this Case, in men over 40 years of age. Epidemiological characteristics, however, do not allow predictability due to the reduced number of cases. 1 The IMT is a soft tissue tumor, which evolves through myofibroblastic differentiation. Its etiology development remains uncertain, but studies suggest possible occurrence secondary to infections, trauma or     pelvic surgeries. When occurs in the genitourinary tract, IMT most often affects the bladder. In this Case, may present nonspecific manifestations, such as dysuria, voiding urgency and low abdominal pain, besides presenting hematuria as the most common manifestation. 2,4 Thus, the case fits the predicted period of onset of symptoms and presents nonspecific evidence like the cases already reported.
For the diagnostic approach, imaging study shows an infiltrating mass, but does not allow the differential diagnosis of the lesion, due to the similarities with malignant neoplasms. Thus, performance of these tests will be important to suggest suspicious lesions, but it becomes secondary in diagnostic confirmation, which depends on biopsy and histological analysis. Microscopic examination will reveal presence of myofibroblastic fusiform cells associated with inflammatory components. 2,3 For treatment, surgical resection remains the best conduct, with the possibility of an open, laparoscopic or transurethral approach. Although transurethral resection of the tumor is more commonly performed, partial laparoscopic cystectomy is related to a lower recurrence rate. 5

Conclusion
IMT is a benign lesion that has similarities with invasive tumors. Because it is a rare condition, there are no defined protocols for the diagnostic and therapeutic approach. Thus, Case reports are a relevant way to contribute to the advancement of knowledge about such a condition. This report highlights the importance of adequate identification of the pathology to avoid misguided interventions.

Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.