Inflammatory myofibroblastic tumour of the bladder

Definition

Inflammatory myofibroblastic tumour was first identified in the lung, but is now known to occur at a range of sites. Postoperative spindle cell nodule is a similar lesion occurring after a surgical procedure⁴.

Synonyms

Inflammatory pseudotumour, pseudosarcomatous fibromyxoid tumour, nodular fasciitis, pseudomalignant spindle cell proliferation, pseudosarcomatous myofibroblastic tumour.

Clinical features

This is usually a tumour of adults, rarely of children⁷. Patients present with haematuria or recurrent cystitis².

Macroscopic appearance

The tumour may be polypoidal or form a submucosal mass². The tumour commonly appears gelatinous².

Histopathology

This is a variably cellular spindle cell tumour. Stellate cells are seen. As at other sites, three patterns occur. Most cases show mix of patterns⁷. There are mitoses (3 to 38/10 HPF⁷) but no abnormal mitotic figures. Atypia is lacking. There may be limited necrosis⁷. There is a mixed inflammatory infiltrate.

Immunohistochemistry (with differential diagnoses for comparison)

	Inflammatory myofibroblastic tumour	postoperative spindle cell nodule	Sarcomatoid carcinoma	Stromal tumour of unknown malignant potential of the prostate	Rhabdomyosarcoma	Leiomyosarcoma	Neurofibroma
ALK-1	8/91, 2/65, 3/46,  12/16 (granular cytoplasmic or linear subplasmalemmal)7		0/51, 0/87	0/27	0/21	0/21, 0/57	0/21
MNF116, Cam5.2 or AE1/3	8/9 (3 diffuse, 5 focal)1, 2/102, 5/154, 13/16 (AE1/3: 13/16, Cam5.2: 9/16)7	2/44	5/5 (all focal)1, 2/34, 6/8 (AE1/3: 6/8, Cam5.2: 2/8)7	0/27	0/21	1/2 (focal)1, 3/84, 0/57	0/21
SMA	8/9 (3 diffuse, 5 focal)1, 3/82, 5/84, 16/167	2/44	4/5 (2 diffuse, 2 focal)1, 2/34, 6/87, 6/87	2/27	0/21	2/2 (1 diffuse, 1 focal)1, 3/74, 5/57	0/21
Desmin	7/9 (all focal)1, 2/92, 3/114, 12/157		2/5 (1 diffuse, 1 focal)1, 0/34, 3/87	2/27	2/21	0/21, 0/84, 3/57
Calponin	8/9 (3 diffuse, 5 focal)1					2/2 (focal)1
Caldesmon	6/9 (2 diffuse, 4 focal)1					2/2 (1 focal, 1 diffuse)1
HHF35	5/84	2/34	1/24			1/54
vimentin	10/102, 10/104	4/44	1/14			7/74
EMA	2/82, 4/84	1/34	1/24			1/84	`
p53	7/104, 14/15 (weak nuclear staining)7	3/44	5/8 (strong staining)7	0/27		9/9 (in addition, there were two negative cases, but these dated from 1928 and 1929, which might account for loss of immunogenicity.)4, 3/5 (strong staining)7
S-100	0/44, 2/157	0/34	0/87	0/27		0/24, 0/57
CD34	0/157		0/87	0/27		1/57
CD117	1/16 (focal weak staining in one case)7		1/87	0/27		1/57

Ultrastructure

The features are those of myofibroblastic cells. Fibronexus junctions are specific to myofibroblastic cells but are not often to be found.

Molecular cytogenetics

• Cytogenetic abnormalities at 2p23, the site of the ALK-1 gene, have been reported⁸. ALK gene translocations examined by FISH are seen in 4 of 6 cases¹.

Differential diagnosis

• Postoperative spindle cell nodule

• Sarcomatoid urothelial carcinoma: may be myxoid. There is marked cytological atypia, abnormal mitoses, non-myxoid areas of greater cellularity. There is often a malignant epithelial component. p53 staining tends to be strong. Staining for cytokeratins may be weak. ALK-1 is negative.

• Leiomyosarcoma: may be myxoid and may show positivity for cytokeratins. A delicate vascular network and an inflammatory infiltrate are lacking. ALK-1 is negative. p53 staining may be strong.

• Rhabdomyosarcoma: positive for myogenin and Myo-D1. May be positive for ALK-1⁹.

See link

Prognosis

The prognosis is good; local resection is adequate. Recurrences may occur, possibly more often in ALK-1 positive cases⁷. Unresected lesions may massively enlarge to cause death by obstruction, not metastasis⁴.

References

¹Freeman, A., N. Geddes, et al. (2004). "Anaplastic lymphoma kinase (ALK 1) staining and molecular analysis in inflammatory myofibroblastic tumours of the bladder: a preliminary clinicopathological study of nine cases and review of the literature." Mod Pathol 17(7): 765-71.

²Jones, E. C., P. B. Clement, et al. (1993). "Inflammatory pseudotumor of the urinary bladder. A clinicopathological, immunohistochemical, ultrastructural, and flow cytometric study of 13 cases." Am J Surg Pathol 17(3): 264-74.

³Coyne, J. D., G. Wilson, et al. (1991). "Inflammatory pseudotumour of the urinary bladder." Histopathology 18(3): 261-4.

⁴Iczkowski, K. A., J. H. Shanks, et al. (2001). "Inflammatory pseudotumor and sarcoma of urinary bladder: differential diagnosis and outcome in thirty-eight spindle cell neoplasms." Mod Pathol 14(10): 1043-51.

⁵Chan, J. K., W. Cheuk, et al. (2001). "Anaplastic lymphoma kinase expression in inflammatory pseudotumors." Am J Surg Pathol 25(6): 761-8.

⁶Cook, J. R., L. P. Dehner, et al. (2001). "Anaplastic lymphoma kinase (ALK) expression in the inflammatory myofibroblastic tumor: a comparative immunohistochemical study." Am J Surg Pathol 25(11): 1364-71.

⁷Tsuzuki, T., C. Magi-Galluzzi, et al. (2004). "ALK-1 expression in inflammatory myofibroblastic tumor of the urinary bladder." Am J Surg Pathol 28(12): 1609-14.

⁸Hojo, H., W. A. Newton, Jr., et al. (1995). "Pseudosarcomatous myofibroblastic tumor of the urinary bladder in children: a study of 11 cases with review of the literature. An Intergroup Rhabdomyosarcoma Study." Am J Surg Pathol 19(11): 1224-36.

⁹Cessna, M. H., H. Zhou, et al. (2002). "Expression of ALK1 and p80 in inflammatory myofibroblastic tumor and its mesenchymal mimics: a study of 135 cases." Mod Pathol 15(9): 931-8.

This page last revised 6.1.2005.

©SMUHT/PW Bishop