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Soft Tissue Pathology 

Pathology of Myofibroblastic Tumours

Dr Sampurna Roy MD            





Myofibroblastic Tumours:

Myofibroblastic tumors. Brief review of clinical aspects, diagnosis and differential diagnosis.

Myofibroblastic tumours: an update.

1. Fibromatosis

2. Infantile digital fibromatosis

3. Infantile myofibromatosis/Myofibroma

4. Angiomyofibroblastoma

5. Intranodal Palisaded Myofibroblastoma

6. Congenital and infantile fibrosarcoma

7. Inflammatory myofibroblastic tumour

8. Low-grade myofibroblastic sarcoma  

9. High grade myofibroblastic sarcoma


Diagnostic Clues: 

- Myofibroblastic tumours are composed of spindle shaped cells set in a collagenous backround.

- The myofibroblastic tumour cells display ill-defined eosinophilic cytoplasm (smooth muscle cells are less pale and more fibrillary), fusiform nuclei and small nucleoli.

- Unlike fibroblasts, myofibroblasts stain positively for muscle actin, smooth muscle actin and/ or desmin.

- Tumour cells in leiomyosarcoma display homogeneous cytoplasmic positivity for actin.

- Neoplastic myofibroblasts display patchy membrane positivity for actin.

- Neoplastic myofibroblasts demonstrate positivity for fibronectin but are negative for heavy caldesmon.

- Neoplasm showing smooth muscle differentiation are positive for heavy caldesmon.

- Neoplastic myofibroblastic cells are negative for S100 protein, cytokeratin and striated muscle markers.


Inflammatory Myofibroblastic Tumour: 

Inflammatory myofibroblastic tumour (inflammatory fibrosarcoma) represents a spectrum of myofibroblastic proliferations.

Meis et al. proposed that some of the intra-abdominal 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 


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. 

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.

Pseudoneoplastic lesions, benign and malignant tumour:
Example: 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.

Further reading:

Inflammatory myofibroblastic tumor of the larynx. A clinicopathologic study of eight cases simulating a malignant spindle cell neoplasm.

Extrapulmonary inflammatory myofibroblastic tumor (inflammatory pseudotumor). A clinicopathologic and immunohistochemical study of 84 cases.

Comparison of DNA ploidy, histologic, and immunohistochemical findings with clinical outcome in inflammatory myofibroblastic tumors. 

Extrapulmonary inflammatory myofibroblastic tumor: a clinical and pathological survey.

Anaplastic Lymphoma Kinase (ALK) Expression in the Inflammatory Myofibroblastic Tumor A Comparative Immunohistochemical Study 

Expression of ALK1 and p80 in Inflammatory Myofibroblastic Tumor and Its Mesenchymal Mimics: A Study of 135 Cases.

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.



Low Grade Myofibroblastic Sarcoma: 

These lesions are usually seen in adults.

However, similar cases have been reported in children.

Commonly located in the deep soft tissue of the oral cavity (tongue), the extremities, the trunk and the abdominal / pelvic cavities.

Microscopically, these are diffusely infiltrative tumour composed of cellular fascicles of spindle-shaped tumour cells displaying myofibroblastic cytological features.

Some cases are hypocellular with a prominent collagenous matrix.

The tumour cells display mild to moderate nuclear atypia wih enlarged hyperchromatic nuclei.

Immunohistochemistry reveals variable actin and desmin positivity ( actin +/ desmin - , actin - / desmin +, or actin + / desmin +)

Most cases stain positively for fibronectin.

Some cases are CD34 and CD99 positive.

S100 protein and epithelial markers are negative.

Differential diagnosis includes benign and malignant spindle cell tumours

Example: Intramuscular myxoma  ; Giant cell fibroblastoma ; desmoid fibromatosis, fibrosarcoma ; malignant peripheral nerve sheath tumour ; low-grade leiomyosarcoma.

Further reading:

Low-grade myofibroblastic sarcoma. Analysis of 18 cases in cases in the spectrum of myofibroblastic tumours. 

High Grade Myofibroblastic Sarcoma: 

High grade (MFH -like) myofibroblastic sarcoma have been reported in children and adults.

In children these are usually located in the head and neck region.

In adults these are common in the extremities.

Salient histological features:

Spindle shaped cells arranged in herringbone or fascicular patterns.

There is abundant collagen production.

Pleomorphic MFH-like areas are present.

Numerous mitotic figures are present.

There are areas of tumour necrosis.

Electron microscopic examination confirms myofibroblastic line of differentiation.

Differential diagnosis:

Histologically it is often extremely difficult to distinguish between myofibroblastic and smooth muscle tumours. Myogenic tumours

Rhabdomyosarcoma (myoglobin, MyoD1,myf-4 are negative in myofibroblastic sarcoma)

Malignant peripheral nerve sheath tumour excluded by electron microscopy and immunohistochemistry

Fibrosarcoma (congenital and infantile and rare examples of adult type)

Further reading:

Myofibrosarcoma: a clinicopathologic study.  


Abstracts :

So-called inflammatory myofibroblastic tumour: a proliferative lesion of fibroblastic reticulum cells?

Inflammatory myofibroblastic tumor with predominant anaplastic lymphoma kinase-positive cells lacking a myofibroblastic phenotype.

Inflammatory myofibroblastic tumour of paranasal sinuses with fatal outcome: reactive lesion or tumour? 

Inflammatory myofibroblastic tumour (inflammatory pseudotumour) of the breast. Clinicopathological and genetic analysis of a case with evidence for clonality. 





Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)






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