| INFLAMMATORY
MYOFIBROBLASTIC TUMOUR:
Inflammatory
myofibroblastic tumour (inflammatory fibrosarcoma) represents a
spectrum of myofibroblastic proliferations.
Meis et al. proposed that some of the intraabdominal tumours which
were previously designated as inflammatory pseudotumour or
inflammatory myofibroblastic tumours where actually sarcomas. However
Coffin et al. suggested that these were benign myofibroblastic
proliferations.
This tumour has potential for recurrence and persistent local growth
.It may progress to frank sarcomatous tumour and metastases have been
recorded. Hence, inflammatory myofibroblastic tumour is best regarded
as a low grade sarcoma.
This tumour is frequently seen in children and adolescents, in
the intra-abdominal and retroperitoneal sites.
Macroscopic features:
The tumour presents as a
solid well circumscribed or a multinodular mass.
Histological features:
(
Three main
histologic patterns: 1. Nodular fasciitis-like 2. Fibrous histiocytoma-like
3. Desmoid or scar tissue-type)
The tumour displays an
admixture of myofibroblasts and fibroblasts arranged in short
interwoven fascicles set in a collagenous stroma. Occasionally,
larger polygonal cells or ganglion-like cells may be present.
A polymorphic inflammatory cell component composed of
lymphocytes and plasma cells are identified in the
backround.
(The backround
stroma may demonstrate three histologic patterns-i) Hypocellular
fibrous: ii) Cellular: iii) Myxoid/vascular )
Immunohistochemistry:
The tumour cells express vimentin, muscle specific actin and
alpha -smooth muscle actin. Focally, the tumour cells are desmin and
cytokeratin positive.
Cytogenetic analysis reveals clonal aberrations usually involving 2p.
There is fusion of the ALK gene with TPM4 and
TPM3 (tropomyosin) genes have been reported and there is
immunohistochemical expression of ALK.
Differential diagnosis:
Calcifying Fibrous Pseudotumor:
Calcifying Fibrous Pseudotumor versus
Inflammatory Myofibroblastic Tumor: A Histological and
Immunohistochemical Comparison. Mod Pathol 2001;14:784-790
Inflammatory
Pseudotumor-Like Follicular Dendritic Cell Tumor:
Inflammatory Pseudotumor-Like
Follicular Dendritic Cell Tumor. A Distinctive Low-Grade Malignant
Intra-abdominal Neoplasm With Consistent Epstein–Barr Virus
Association.Am J Surg Pathol 2001;25:721-731
Pseudoneoplastic
lesions, benign and malignant tumour-
Eg. Pseudosarcomatous
fasciitis-like lesions,
(sclerosing mediastinitis, mesenteritis, retroperitonitis),
Fibrohistiocytic tumours-
(benign
fibrous histiocytoma
,
malignant fibrous histiocytoma
or pleomorphic sarcoma),
Desmoid fibromatosis
,
Inflammatory leiomyosarcoma,
Lymphoma, sarcomatoid carcinoma,
sarcomatoid malignant mesothelioma,
Rhabdomyosarcoma.
Detailed clinical history, histological features and appropriate
immunohistochemical staining helps in excluding these lesions.
IMAGE
LINKS:1 ;
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5(ESCOP)
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