Trucut biopsy needle

This video from YouTube illustrates the use of a Trucut biopsy needle. These needles can be used to obtain specimens of soft tissue tumours, often under ultrasound guidance.

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Dedifferentiated liposarcoma

A dedifferentiated liposarcoma is a soft tissue tumour which shows progression either in the primary tumour or after local recurrence to a sarcoma of variable histological grade, often not lipogenic. Dedifferentiated liposarcoma occurs in up to 10% of well-differentiated liposarcomas, although the risk is higher in the retroperitoneum and lower in the extremities, likely reflecting the longer time taken to detect tumours in the former location.

Dedifferentiated liposarcomas are most common in the retroperitoneum, but can occur in the spermatic cord or rarely head and neck and trunk. They are extremely rare in subcutaneous tissues. These tumours usually present as a painless mass, with both lipomatous and non-lipomatous elements on MRI scanning. Some present with an increase in size of a long-standing tumour, suggestive of dedifferentiation.

Dedifferentiated areas are variable histologically, but can resemble undifferentiated pleomorphic sarcoma or myxofibrosarcoma. Tumours most often contain ring or giant marker chromosomes.

After treatment, local recurrence can occur in up to 40% of cases, particularly in the retroperitoneum. Tumours exhibit a less aggressive clinical course than other types of high grade pleomorphic sarcoma, with metastases in 15-20% of cases and a overall mortality of 28-30% at 5 years.

 

1. WHO Classification of Tumours of Soft Tissue and Bone. 4th Edition, 2013.

Atypical lipomatous tumour

An atypical lipomatous tumour is a locally aggressive mesenchymal neoplasm in which the adipocytes show significant variation in cell size and have some nuclear atypia. These tumours are at risk of local recurrence. In the extremities or trunk the term atypical lipomatous tumour is justified as complete excision is usually curative and local recurrence manageable. In the retroperitoneum or mediastinum however, tumours with the same biological composition are difficult to completely remove and can recur with disastrous consequences for the patient. In these locations, the term “well-differentiated liposarcoma” may therefore be more appropriate.

Atypical lipomatous tumours account for 40-45% of all liposarcomas and occur predominantly in middle aged adults, peaking in the sixth decade. They most frequently occur in the deep soft tissues of the limbs, especially the thigh, but may also occur in the retroperitoneum or paratesticular area. Tumours often grow slowly, are painless and can achieve significant sizes.

Anatomical location is the most important prognostic factor. Lesions in surgically resectable sites tend not to recur after complete excision. In more difficult anatomic sites, incomplete excision is associated with local recurrence, which in turn can lead to loss of local control, or be associated with dedifferentiation and death. The risk of dedifferentiation is said to be over 20% in the retroperitoneum, but <2% in the limbs.

1. WHO Classification of Tumours of Soft Tissue and Bone. 4th Edition, 2013.

Staging for soft tissue sarcoma

As well as the MSTS system for staging soft tissue sarcoma, there is an established American Joint Committee on Cancer Staging (AJCC) TNM system. This is in its seventh version.

Staging investigations typically involve local site imaging and CT of chest, possibly including the abdomen and pelvis. Nodal involvement is unusual, but may be more common in some types, such as clear cell sarcoma, epithelioid sarcoma and rhabdomyosarcoma.

The size cut off between T1 and T2 is 5cm, above which tumours are considered T2. Tumours above and not involving the deep fascia are considered superficial,  those involving or deep to the fascia are considered deep.

 

Definitions for staging

TX

Primary tumor cannot be assessed.

T0

No evidence of primary tumor.

T1

Tumor ≤5 cm in greatest dimension. (Size should be regarded as a continuous variable, and the measurement should be provided.)

T1a

Superficial tumor.b

T1b

Deep tumor.b

T2

Tumor >5 cm in greatest dimension.b

T2a

Superficial tumor.b

T2b

Deep tumor.

 

NX

Regional lymph nodes cannot be assessed.

N0

No regional lymph node metastasis.

N1b

Regional lymph node metastasis.

 

M0

No distant metastasis.

M1

Distant metastasis.

 

Stage IA

T1a

N0

M0

G1, GX

T1b

N0

M0

G1, GX

Stage IB

T2a

N0

M0

G1, GX

T2b

N0

M0

G1, GX

Stage IIA

T1a

N0

M0

G2, G3

T1b

N0

M0

G2, G3

Stage IIB

T2a

N0

M0

G2

T2b

N0

M0

G2

Stage III

T2a, T2b

N0

M0

G3

Any T

N1

M0

Any G

Stage IV

Any T

Any N

M1

Any G

 

Reference:

 AJCC: Soft tissue sarcoma. In: Edge SB, Byrd DR, Compton CC, et al., eds.: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer, 2010, pp 291-8.

 

 

 

Myxofibrosarcoma

Myxofibrosarcomas are soft tissue malignant tumours that are grossly and microscopically nodular and mucoid in appearance. They tend to occupy subcutaneous sites, that characteristically have a large vascular network with rapid circulation (Kindblom et al., 1977, Fletcher et al., 2002).  The differential diagnosis includes other soft tissue sarcomas such as leiomyosarcoma and liposarcoma (Mutter et al., 2011).

These tumours tend to occur in the elderly population, commonly affecting the extremities (lower > upper), and are typically prevalent in male patients aged sixty to eighty years (Fletcher et al., 2002, Sanfilippo et al., 2011).  Their presentation is often that of a painless slowly growing mass.

The risk of distant metastases is generally lower than for other soft tissue sarcomas.  Metastatic sites include lung, bone and lymph nodes, with histological grade being the main risk factor for metastasis (Mentzel, 2011, Sanfilippo et al., 2011).

Myxofibrosarcomas tend to grow by tracking along fascial planes, which can be manifested on MRI by a high signal “tail” which contains tumour (Kaya et al., 2008). Even in the absence of this appearance, these tumours tend to grow in an infiltrative fashion. The risk of local recurrence is consequently high compared to other sarcomas (31% in one series (Haglund et al., 2010)). When it occurs, local recurrence is associated with more chromosomal aberrations and a higher histological grade, so increasing the likelihood of invading distant sites; overall survival at five years has been reported as being 60-77% (Fletcher et al., 2002, Willems et al., 2006, Sanfilippo et al., 2011).

Management should be multidisciplinary, with a surgical approach emphasising negative margins. As with other soft tissue sarcomas, adjuvant radiotherapy may be useful  (Mutter et al., 2011, Sanfilippo et al., 2011).

 

Christopher Ghazala, Craig Gerrand

References

Fletcher C, Unni K, Mertens F (2002) World Health Organization classification of tumours. Pathology and genetics of tumours of soft tissue and bone. Lyon, France: IARC Press.

Haglund K,  Raut CP,  Nascimento AF, Wang Q, George S, Baldini EH (2010)  Recurrence Patterns and Survival for Patients with Intermediate- and High-Grade Myxofibrosarcoma. International journal of radiation oncology, biology, physics 18 October 2010 (Article in Press DOI: 10.1016/j.ijrobp.2010.08.042)

Kindblom LG, Merck C, Svendsen P (1977) Myxofibrosarcoma: a pathologico-anatomical, microangiographic and angiographic correlative study of eight cases. Br J Radiol 50:876-887.

Kaya M, Wada T, Nagoya S, Sasaki M, Matsumura T (2008)  MRI and histological evaluation of the infiltrative growth pattern of myxofibrosarcoma. Skeletal Radiol (2008) 37: 1085.

Mentzel T (2011) Sarcomas of the skin in the elderly. Clinics in Dermatology 29:80-90.

Mutter RW, Singer S, Zhang Z, Brennan MF, Alektiar KM (2011) The enigma of myxofibrosarcoma of the extremity. Cancer.

Sanfilippo R, Miceli R, Grosso F, Fiore M, Puma E, Pennacchioli E, Barisella M, Sangalli C, Mariani L, Casali P, Gronchi A (2011) Myxofibrosarcoma: Prognostic Factors and Survival in a Series of Patients Treated at a Single Institution. Annals of Surgical Oncology 18:720-725.

Willems SM, Debiec-Rychter M, Szuhai K, Hogendoorn PCW, Sciot R (2006) Local recurrence of myxofibrosarcoma is associated with increase in tumour grade and cytogenetic aberrations, suggesting a multistep tumour progression model. Mod Pathol 19:407-416.

Incidence and epidemiology of soft tissue sarcoma

Soft tissue sarcomas occur with an incidence of 30 per million and represent less than 1% of all malignancies. They can occur in almost any anatomic site, but tend to occur with a frequency that reflects the volume of mesechymal-derived tissue in that region.  For example, around 55% occur in the limbs. The type of tumour varies with age: rhabdomyosarcoma is a disease of early life, whereas leiomyosarcoma is more common in the elderly.

Environmental factors associated with sarcoma include:

  • Radiation (eg after therapeutic radiotherapy)
  • Immunodeficiency
  • Occupational (eg exposure to dioxins)

Genetic factors include

  • Li-Fraumeni syndrome (inherited p53 deficiency)
  • Neurofibromatosis.

Classification of soft tissue tumours

Soft tissue tumours are classified using the WHO classification, based on the morphological appearances of the tumour and whether or not it is benign or malignant. There are more than 50 variants of soft tissue sarcoma. The classification includes:

  • adipocytic tumours (eg lipoma, liposarcoma)
  • fibroblastic/myofibroblastic tumours (eg elastofibroma, adult fibrosarcoma)
  • so-called fibrohistiocytic tumours (eg GCT of tendon sheath, pleomorphic MFH)
  • smooth muscle tumours (eg angioleiomyoma, leiomyosarcoma)
  • pericytic tumours (eg glomus tumour)
  • skeletal muscle tumours (eg rahbdomyoma, rhabdomyosarcoma)
  • vascular tumours (eg haemangioma, angiosarcoma)
  • chondro-osseous tumours (eg soft tissue chondroma, extraskeletal osteosarcoma)
  • tumours of uncertain differentiation (eg intramuscular myxoma, synovial sarcoma)