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Soft Tissue Pathology 

An Approach to Histopathological Reporting of Soft Tissue Tumour

Dr Sampurna Roy MD 





The pathologist should answer the following questions in a step-wise manner before making the final diagnosis:

Is it a primary tumour?

Could it be an inflammatory process (Example: Pseudotumour or abscess) ? 

Is it a metastatic tumour or involvement by lymphoma or leukaemia?

Is it a pure soft tissue tumour or a lesion like spindle cell carcinoma?

Does the tumour have any recognizable differentiation?            

Is it benign, locally aggressive but non-metastasizing or malignant?

Is the excision complete with adequate margins?

Are there any other histological prognostic data present?  

The following clinical details should be provided by the clinician:

I  About the patient 

Age and sex
Preoperative symptoms
Previous medical or surgical history

II  About the tumour 

Location including anatomical planes (Cutanous, subcutaneous or deep)

Superficial soft tissue - Benign tumours and rarely sarcomas (myxoid MFH and leiomyosarcoma)

Deep fascia - Sarcoma

Size and duration - Example: Sarcoma is larger with longer history.

Fasciitis is smaller and of recent onset.

Any history of pain or tenderness.

Whether single or multiple,

Whether underlying structures are involved,  

Whether rapid or slow  growing tumour.


The histopathology report should include the following features:

Histological Patterns : 

Spindle cell







Mixed patterns


1.  Hyaline

2.  Fibrous

3.  Myxoid

4.  Osteocartilaginous

Cytoplasmic Features:

I.  Cytoplasmic stain: 

1. Eosinophilic -Indicate smooth muscle , myofibroblastic or fibrohistiocytic forms

2. Basophilic - Suggest neural , fibroblastic or synovial forms.

II. Cytoplasmic vacuoles:

1. Intracytoplasmic vacuoles with RBCs - Epithelioid vascular tumour

2. Well defined vacuoles indenting the nucleus - Lipoblasts.

III Cytoplasmic inclusion:   

1. Eosinophilic round inclusions (actin)-Infantile digital fibroma.

2. PAS positive crystalline structures-Alveolar soft part sarcoma.

Nuclear Features:  

I Shape: 

1. Cigar shaped- Smooth muscle tumour

2. Wavy with pointed end-  Neural tumour

3.Tapered,pointed ends- Fibroblasts

4. Ovoid, crenated ; small distinct  nucleolus - Myofibroblast  
II. Chromatin:

Hyperchromatic dense chromatin-
Example -  degenerative changes in
neural and adipocytic tumours

Giant cells:

Giant cells are noted in some soft tissue tumours:


Mutinucleated lipoblasts - Liposarcoma

Ganglion like giant cells- Proliferative myositis /fasciitis

Floret giant cells- Pleomorphic lipoma

Wreath like giant cells- Alveolar  rhabdomyosarcoma

Touton giant cell- Juvenile xanthogranuloma

Vascular Pattern:

1. Chicken wire or crow's feet  branching- Myxoid liposarcoma

2. Staghorn branching- Haemangiopericytoma

3. Hyaline vesselsSchwannoma, aggressive angiomyxoma

4. Sieve-like space-  Kaposi's  sarcoma, Spindle cell haemangioendothelioma

Mitotic count: 

Numerous bizarre mitotic figures may be present in a benign tumour like atypical fibroxanthoma.

Mitotic count may be low in a high grade malignant tumour like round cell liposarcoma

Any mitosis in neurofibromatous tumour implies malignancy, in contrast  fairly numerous mitoses is noted in cellular schwannoma.

Mitoses is the main criteria for the diagnosis of malignancy in smooth muscle tumour.

Edge of tumour:

1. True or pseudocapsule
2. Well circumscribed or infiltrative margin.

Adequacy of Excision:

In all locally aggressive and malignant tumours it is essential  to comment on adequacy of excision.

Local recurrence may occur in case of sarcomas where the excision margins are less than 1-2 cm.

Other features:

1. Multicentricity

2. Necrosis

3. Vascular invasion

4. Cystic change



Spindle cell carcinoma can be ruled out by appropriate immunostains. 

Desmoplastic melanoma can closely resemble many sarcomas specially leiomyosarcoma , MPNST and pleomorphic sarcoma (MFH).

Soft tissue lymphoma must be considered in any large round cell tumour in soft tissue.

Criteria of malignancy depends on the cell type:

Smooth muscle tumour  - Presence of  mitoses or necrosis in deep lesions are consistent with  malignancy.

Nerve sheath tumour - Encapsulation and widespread S100 protein positivity are indicative of cellular schwannoma.

Myofibroblastic tumours- pleomorphism, cytologic and mitotic atypia with large nucleoli and necrosis indicate malignancy.

Light microscopy is usually the only useful technique for distinguishing reactive lesions or benign tumours from malignant tumours.

Examples :

Well differentiated liposarcoma may have areas resembling its benign counterpart.

Fibromatosis can be difficult to distinguish from low grade sarcoma.


PAS is positive-

-Granular cell tumour

-Epithelial mucin in biphasic synovial sarcoma.

-Glycogen in smooth and skeletal muscle tumour, chondroid tumours and liposarcoma

-Diastase resistant inclusions in alveolar soft part sarcoma.

Alcian blue for sulphated mucin in Myxoid chondrosarcoma.

Masson trichrome - Collagen and muscle

PTAH- Cross striations in rhabdomyosarcoma.

Reticulin- Demonstrate architecture and vascular pattern.

Following tumours may be under- diagnosed as a benign lesions :

Malignant tumours like epithelioid sarcoma, low grade fibromyxoid sarcoma and myxofibrosarcoma, atypical lipomatous tumour and well differentiated leiomyosarcoma.             

This may be avoided by:

1. Careful assessement of architecture, cytological character, tumour stromal interphase and associated reaction ;

2. Immunohistochemical findings ;

3. Awareness of other diagnostic possibilities.

Following reactive soft tissue lesion may be overdiagnosed as sarcomas:

Nodular fasciitis and its variants ;

Proliferative fasciitis;

Proliferative myositis;  

Myositis ossificans,

Fracture callus.


Cytokeratin- (EMA and pancytokeratin) -Epithelial marker.

Desmin, smooth muscle actin display muscle differentiation.

CD31 and von Willebrand factor- vascular marker

LCA, B and T cells markers - Lymphoid Tumour Marker

S100 protein - Demonstrate neural, adipocytic, and cartilaginous differentiation.

HMB45 - Demonstrate  clear cell sarcoma and angiomyolipoma.

CD99, neuron specific enolase, (NSE) and PGP 9.5- primitive neuroectodermal tumours/Ewing's sarcoma.

CD34- dermatofibrosarcoma protuberans and solitary fibrous tumour

Myoglobin- Display skeletal muscle differentiation.


Soft Tissue Tumour Online

Classification of Soft Tissue Tumour

Grading of soft tissue tumours

Gross examination of soft tissue specimen

Lipomatous tumours

Neural tumours

Myogenic tumours

Vascular tumours

Fibroblastic/Myofibroblastic tumours

Myofibroblastic tumours

Fibrohistiocytic tumours

ChondroOsseous tumours

Soft Tissue Tumours of Uncertain Differentiation 

Notochordal Tumour - Chordoma





Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)






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