Inflammatory Pseudotumor and Sarcoma of Urinary Bladder: Differential Diagnosis and Outcome in Thirty-Eight Spindle Cell Neoplasms

Abstract

We assessed diagnostic criteria among 38 spindle cell tumors of the urinary bladder and obtained follow-up in 36 patients. Patients comprised 28 males and 10 females aged 2.5 months to 87 years. Hematuria was the commonest presenting symptom (27 patients). After review and immunohistochemical workup, 17 patients had inflammatory pseudotumor (myofibroblastic tumor), 4 postoperative spindle cell nodule, 1 leiomyoma, 13 sarcoma (7 low-grade; 6 high-grade), and 3 carcinoma. Mean age was 38 years for pseudotumor (range 15 to 74), 65 for postoperative spindle cell nodule, 51 for sarcoma, and 76 for carcinoma. Size of pseudotumor averaged 4.4 ؎ 0.7 cm (range 1.5 to 13.0), similar to sarcoma, 4.0 ؎ 0.6 cm (range 0.5 to 7.0). Similar proportions of benign tumors and sarcomas had muscularis propria invasion. The criteria that best differentiated sarcoma from inflammatory pseudotumor were presence of necrosis at the tumordetrusor muscle interface in muscle-invasive cases, and nuclear atypia. Sarcoma also had less prominent microvasculature, less variable cellularity, consistently >1 mitotic figure per 10 high-power fields, and predominant acute inflammation without plasma cells. p53 protein nuclear immunostaining was moderate, unlike the rare to absent staining in pseudotumors. Because all 12 sarcomas were desmin-negative, we did not call them leiomyosarcoma; they overlapped with benign tumor in epithelial, mesenchymal, and actin immunostaining. Among 12 sarcoma patients, 2 died of tumor (at 3 months). Two of four experienced tumor recurrence after partial cystectomy (2 and 26 months). No pseudotumors recurred after transurethral resection or partial cystectomy, although one patient, 5 months after transurethral resection, had histologically identical pseudotumor that the surgeon considered residual. Another patient with pseudotumor, not a candidate for tumor ablation after transurethral resection, had continued tumor growth and he died of urosepsis. In conclusion, inflammatory pseudotumor, although overlapping with sarcoma in presentation, age range, and size, does not metastasize and remains histologically distinct from low-grade sarcoma.

Utility of ALK-1 protein expression and ALK rearrangements in distinguishing inflammatory myofibroblastic tumor from malignant spindle cell lesions of the urinary bladder

“…3,6,7,[10][11][12][13][14]16,17 Both epithelial and myogenic markers can be expressed in inflammatory myofibroblastic tumor and may lead to a misdiagnosis of sarcomatoid carcinoma, leiomyosarcoma or rhabdomyosarcoma. 6,7,11,13 This study confirms the utility of the detection of ALK-1 protein by immunoperoxidase methods and ALK rearrangements by FISH and the limited value of immunohistochemical markers for epithelial, myogenic and follicular dendritic differentiation in the separation of inflammatory myofibroblastic tumors from malignant spindle cell tumors of the urinary bladder.…”

“…3,6,7,[10][11][12][13][14]16,17 Both epithelial and myogenic markers can be expressed in inflammatory myofibroblastic tumor and may lead to a misdiagnosis of sarcomatoid carcinoma, leiomyosarcoma or rhabdomyosarcoma. 6,7,11,13 This study confirms the utility of the detection of ALK-1 protein by immunoperoxidase methods and ALK rearrangements by FISH and the limited value of immunohistochemical markers for epithelial, myogenic and follicular dendritic differentiation in the separation of inflammatory myofibroblastic tumors from malignant spindle cell tumors of the urinary bladder. Originally identified as a protein overexpressed in anaplastic large-cell lymphoma, ALK-1 has subsequently been shown to be overexpressed in a substantial proportion of inflammatory myofibroblastic tumors of various anatomic locations, [1][2][3][4][5][6][7][8][9]15 including the urinary bladder.…”

“…Histologically, inflammatory myofibroblastic tumor is characterized by a proliferation of spindled cells arranged in loose, variably cellular fascicles admixed with inflammatory cells including plasma cells, and lymphocytes. 3,6,7,[10][11][12][13] In the urinary bladder, as in other sites, these tumors can exhibit infiltrative growth, increased cellular density, cytologic atypia, mitotic activity, mucosal ulceration and necrosis, mimicking malignant spindle cell tumors such as leiomyosarcoma, sarcomatoid carcinoma and rhabdomyosarcoma. 3,6,7,[10][11][12][13][14] Additionally, inflammatory myofibroblastic tumor shares immunophenotypic features with these malignant tumors, including the expression of cytokeratins, smooth muscle antigens and desmin.…”

“…3,6,7,[10][11][12][13] In the urinary bladder, as in other sites, these tumors can exhibit infiltrative growth, increased cellular density, cytologic atypia, mitotic activity, mucosal ulceration and necrosis, mimicking malignant spindle cell tumors such as leiomyosarcoma, sarcomatoid carcinoma and rhabdomyosarcoma. 3,6,7,[10][11][12][13][14] Additionally, inflammatory myofibroblastic tumor shares immunophenotypic features with these malignant tumors, including the expression of cytokeratins, smooth muscle antigens and desmin. 3,10,11,13,[15][16][17] The morphologic and immunophenotypic similarities between inflammatory myofibroblastic tumor and malignant urinary bladder tumors can lead to a misdiagnosis of inflammatory myofibroblastic tumor as a highly malignant tumor, resulting in unnecessary radical surgery.…”

“…3,6,7,[10][11][12][13][14] Additionally, inflammatory myofibroblastic tumor shares immunophenotypic features with these malignant tumors, including the expression of cytokeratins, smooth muscle antigens and desmin. 3,10,11,13,[15][16][17] The morphologic and immunophenotypic similarities between inflammatory myofibroblastic tumor and malignant urinary bladder tumors can lead to a misdiagnosis of inflammatory myofibroblastic tumor as a highly malignant tumor, resulting in unnecessary radical surgery. Therefore, there is need for a more specific marker of inflammatory myofibroblastic tumor.…”