Inflammatory pseudotumor of the urinary bladder with an aberrant expression of cytokeratin

Abstract

A case of inflammatory pseudotumor of the urinary bladder in a 47 year old Japanese male patient is presented. Inflammatory pseudotumor of the urinary bladder is a benign but rare proliferative lesion of the submucosal stroma, easily mistaken for a malignant neoplasm. Based on the clinical diagnosis of bladder cancer by cystoscopy and magnetic resonance imaging (MRI), urologists started chemotherapy before results of the histological report were available which described inflammatory pseudotumor on the biopsy. Biopsied materials showed marked proliferation of irregularly bundled spindle cells, varied in size and shape and separated in severe loose myxoid stroma with moderate infiltration of the inflammatory cells and capillary proliferations. At a glance, these findings resemble the sarcomatous pattern. However neither severe nuclear atypism nor atypical mitoses were present. Immunohistochemically, these spindle cells, which were positive for vimentin and alpha-smooth muscle actin, showed a diffuse aberrant expression of cytokeratin. Some of them were positive for phosphotungstic acid hematoxylin. Electron microscopy revealed only the fibroblasts. No recurrence has been observed for 10 months. These findings indicate that inflammatory pseudotumor is a benign mesenchymal lesion that must be discriminated from true sarcoma to avoid subjecting the patient to unnecessary therapy. Only careful histological examination can enable a successful diagnosis.

Papillary Clusters as a Diagnostic Pitfall in Urinary Cytology of Pseudosarcomatous Fibromyxoid Tumor of the Bladder

“…5 However, aberrant expression of cytokeratins, as in our case, and epithelial membrane antigen have been reported. 5,6,19 This case was described because of the typical appearance of PFT of the urinary bladder. The presence of numerous papillary cell clusters with prominent nucleoli on urinary cytology warrants consideration of TCC in the differential diagnosis.…”

“…Pseudosarcomatous fibromyxoid tumor (PFT) of the urinary bladder is a relatively recently described disease with distinctive histologic features that make it a separate entity. The term PFT was coined in 1986 by Ro 15 for a tumor that also goes by the name of inflammatory pseudotumor, 2,6,9,13,20 nodular fasciitis of the bladder, 1 spindle cell proliferation, 22 sclerosing inflammatory pseudotumor, 8 pseudosarcomatous myofibroblastic proliferation 18 and reactive pseudosarcomatous response. 17 However, the term inflammatory pseudotumor caused much misunderstanding and argument, leading to the now-well-accepted PFT.…”

Inflammatory Pseudotumor of the Urinary Bladder with Aberrant Expression of Cytokeratin

“…It is manifested by nodular, submucosal proliferation of spindle cells of varying sizes and shapes, occasionally leading to the erroneous diagnosis of sarcoma. These proliferating cells exhibit features of fibroblastic and myofibroblastic differentiation on immunocytochemical 6,8,9,14 and ultrastructural examinations. 6,8,14 Inflammatory pseudotumor of the urinary bladder has been assigned various terms, including reactive pseudosarcomatous response, 15 nodular fasciitis of the bladder 2 and pseudosarcomatous fibromyxoid tumor.…”

“…These proliferating cells exhibit features of fibroblastic and myofibroblastic differentiation on immunocytochemical 6,8,9,14 and ultrastructural examinations. 6,8,14 Inflammatory pseudotumor of the urinary bladder has been assigned various terms, including reactive pseudosarcomatous response, 15 nodular fasciitis of the bladder 2 and pseudosarcomatous fibromyxoid tumor. 14 Although > 40 cases of this lesion have been reported in the literature, 6,8 cases with detailed cytologic findings are rare.…”

“…6,8,14 Inflammatory pseudotumor of the urinary bladder has been assigned various terms, including reactive pseudosarcomatous response, 15 nodular fasciitis of the bladder 2 and pseudosarcomatous fibromyxoid tumor. 14 Although > 40 cases of this lesion have been reported in the literature, 6,8 cases with detailed cytologic findings are rare. 12 We report here an additional case of this disease with urine and imprint cytologic features as well as histologic, immunocytochemical and cytogenetic findings.…”