Soft tissue lesions

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Soft tissue lesions strike fear in many pathologists as they are uncommon and may be difficult to diagnose.

Bone tumours are dealt with in the bone article.

WHO classification of soft tissue lesions/tumours

Morphologic grouping[1]

  1. Adipocytic tumours.
  2. Fibroblastic/myofibroblastic tumours.
  3. "Fibrohistiocytic" tumours.
  4. Smooth muscle tumours.
  5. Skeletal muscle tumours.
  6. Vascular tumours.
  7. Perivascular (pericytic) tumours.
  8. Chondro-osseous tumours.
  9. Tumours of uncertain differentiation.

Biologic potential grouping[2]

  1. Benign.
  2. Intermediate (locally aggressive).
  3. Intermediate (rarely metastasizing).
  4. Malignant.

Prevalence

  • All sarcomas are rare buggers.
    • As the classification has been changing over the past years (with more subtypes being recognized/identified) numbers are variable from study-to-study.
  • Once upon a time almost everything was called malignant fibrous histiocytoma; thus, it is listed as a common entity in some publications.

Most common:[3]

  • Liposarcoma.
  • Leiomyosarcoma.

Molecular testing

  • Molecular testing plays an important role in soft tissue pathology.
  • It is generally seen as an adjunct test that:[4]
    • Often is used to confirm the histomorphologic impression/quality control.
    • Frequently has some prognostic significance.
    • May directly affect treatment.

Other

Neurofibromatosis

Comes in two flavours:

  1. NF1 (peripheral).
  2. NF2 (central).

NF1

Features (need 2/7 to diagnose):[5]

  • Two or more neurofibromas or one plexiform neurofibroma.
  • Café-au-lait spots.
  • Freckles in axilla or inguinal area.
  • Optic nerve glioma.
  • Iris hamartomas (Lisch nodules).
  • Sphenoid dysplasia or typical long-bone abnormalities (e.g. bowing).
  • First-degree relative with NF1.

NF2

Features (need 1/3 to diagnose):[6]

  1. Bilateral CNVIII masses on imaging.
  2. Unilateral CNVIII mass + first-degree relative with NF2.
  3. First-degree relative with NF2 and 2/4 of the following:
    1. Meningioma.
    2. Glioma.
    3. Schwannoma.
    4. Juvenile cataract.

Small round blue cell tumours (SRBCT)

A group of tumours that has a similar histologic appearance. It is a group of tumours that is seen more often in childhood than adulthood.

DDx

  • Neuroblastoma.
  • Wilm's tumour.
  • Alveolar rhabdomyosarcoma.
  • Ewing sarcoma/PNET - this entity is dealt with in the bone article.
  • Lymphoma (diffuse large B cell lymphoma).
  • Retinoblastoma.
  • Hepatoblastoma.
  • Desmoplastic small round cell tumour.

Microscopic

Features:

  • Sheets of cells, very cellular.
  • Small cells ~ 2X RBC diameter.
  • Scant cytoplasm.
  • Coarse chromatin.
  • Nucleolus (???).
  • +/-Vascular.

Adipocytic tumours

Hibernoma

General

  • Consists of brown fat (present in the infants to generate heat).[7]
  • Benign.
  • Usually asymptomatic.[8]

Epidemiology

  • Young adults.

Gross

  • Well-circumscribed.
  • Lobulated and light-brown on sectioning.

Microscopic

Features:[9]

  • Large polygonal/oval cells:
    • Nucleus - central & small.[10]
      • Nucleoli typically prominent.[11]
    • Cytoplasm - multivacuolated, oval, eosinophilic, granular.

Image:

Liposarcoma

  • Most common malignant sarcoma in the retroperitoneum.

Microscopy

Features:

  • Lipoblasts:
    • Large sharply demarcated vacuole.
    • Nucleus:
      • Hyperchromatic (dark staining) nucleus.
      • Eccentric location.
      • Nuclear indentation.

Images:

IHC

  • IHC is of limited value.
  • S-100 +ve ~1/3 of the time.
  • Reticulin ???.

Smooth muscle tumours

Leiomyosarcoma

See gyne notes.

Microscopy

Features:

  • Nuclear atypia.
  • Necrosis.
  • Mitoses.

Fibroblastic/myofibroblastic tumours

Proliferative fasciitis

  • Need to write something here.

Solitary fibrous tumour

General

  • Grouped with hemangiopericytoma in the WHO classification; possibly the same tumour (?).[12]
  • May be benign or malignant; more commonly benign.[13][14]

Hemangiopericytoma

General

  • Grouped with solitary fibrous tumour in the WHO classification; possibly the same tumour (?).[12]
  • Arises from the pericyte, a connective tissue cell of small vessels that is thought to be involved in flow regulation.
  • Hematologic spread most common - to lungs.[15]
  • Oncogenic osteomalacia - assoc. with hemangiopericytoma.[16]

Presentation

  • Usually painless mass, slow enlargement.

Radiology

  • Intramedullary lytic mass.
  • May be well-circumscribed.
  • +/-Periosteal reaction.
  • +/-Sclerotic border.

May be worked-up with angiography to distinguish from a vascular malformation.[17]

Location

  • Usually extremities - femur or prox. tibial.[18]

Histology

Features:[19]

  • Hypervascular lesion - key diagnostic feature.[20]
    • Abundant thin-walled branching small vessels of variable size.
      • May be described as "staghorn vessels" or "antler-like" vasculature.
      • Cells may "onion-skin" around thin blood vessels.
  • Spindle or ovoid shaped cells in nests or sheets.

IHC

Features:[21][20]

  • Vimentin +ve (usually).
  • Desmin -ve (typical).
  • Factor VIII -ve (marks endothelium).
  • CD34 +ve.
    • CD34 usu. -ve in synovial sarcoma.
  • CD31 -ve (marks benign endothelium).
  • vWF (von Willebrand factor) -ve.

DDx

  • Other vascular tumours.
  • Vascular malformations.
  • Synovial sarcoma.

Desmoplastic fibroblastoma

  • AKA collagenous fibroma.[22]
  • Benign lesion.
  • Classically found in shoulder region.

IHC

  • Beta-catenin -ve.[23]
    • Significance ???

Vascular tumours

Kaposi sarcoma

General

  • Not really a sarcoma.
  • Caused by HHV-8.
  • Associated with immunodeficiency, e.g. HIV/AIDS.

Stages

It is seen in different stages:[24]

  1. Patch stage.
  2. Plaque stage.
  3. Nodular stage.
  4. Lymphangioma-like. (???)

Microscopic

Features:[25]

  • Vascular channels that anastomose - key feature.
  • +/-Nuclear atypia.
  • Hyaline globules (intracytoplasmic)[26] - pale pink globs (that are paler than RBCs) - important feature.
  • +/-Hemosiderin deposits.

DDx:

  • Angiosarcoma (have many mitoses).

Notes:

  • Hyaline globules have a DDx (hepatocellular carcinoma, lung adenocarcinoma, chondrosarcomas + others).[26]

Images:

IHC

  • CD31 +ve.
  • CD34 +ve.
  • HHV-8 +ve.

Angiosarcoma

General

  • Malignant tumour.

Microscopic

Features:

  • Very many small capillaries or irregular shape lined with:
    • Atypical nuclei, pleomorphic nuclei.
  • Mitoses.
  • Cytoplasmic vacuoles.
    • Cells trying to form lumina - embryologic.

Hemangioendothelioma

General

  • Usually benign.

Microscopic

Features:[27]

  • Well-formed thin vascular channels on a fibrous stroma - key feature.
  • +/-Thrombosis.
  • +/-Calcification.
  • +/-Fibrosis.
  • +/-Myxoid change.

IHC

  • Factor VIII +ve.

Skeletal muscle tumours

Rhabdomyosarcoma

  • Often abbreviated RMS.
  • Most common paediatric sarcoma.
  • ~6% of all childhood cancer.

Histological subdivision:

  1. Alveolar rhabdomyosarcoma.
    • Usually young adults/adolescents.
    • Early mets common.
  2. Embryonal rhabdomyosarcoma.
    • Usual <10 years old.
    • Typically locally invasive.

Molecular and histologic subdivision:

  1. Translocation-positive alveolar RMS.
  2. Translocation-negative alveolar RMS.
  3. Embryonal RMS.

Notes:

  • Translocation-negative alveolar RMS shares characteristics with embryonal RMS.

Microscopy

Alveolar rhabdomyosarcoma:

  • Alveolus-like pattern:
    • Fibrous septae lined by tumour cells.
      • Space between fibrous sepate may be filled with tumour: solid variant of alveolar rhabdomyosarcoma.
  • Eccentric nucleus (???).
  • Cytoplasm - dense pink staining on H&E (if well differentiated).
  • Usu. nuclear pleomorphism +++.
  • Mitoses common.

Molecular diagnostics

Alveolar rhabdomyosarcoma

Common translocations (~80%):

  • t(1,13).
    • PAX3/FKHR fusion gene.
  • t(2,13).
    • PAX7/FKHR fusion gene.

Several uncommon translocations exist.

IHC

  • Desmin (best marker).
  • Actin.

Tumours of uncertain differentiation

Clear cell sarcoma

  • Known among pathologists as "soft-tissue melanoma" and "melanoma of the soft parts", as it has a strong morphological resemblance.[28]
    • Molecular changes and origin distinct from melanoma.
  • Incidence: rare soft tissue tumour.

Clinical

  • Usually - deep soft tissue or extremities.
  • Guarded prognosis.
  • First described in 1965.[29]

Microscopy

Features:[28]

  • Architecture: sheets or fascicular (bundles) arrangement.
  • Cells: Spindle cells or epithelioid cells.
  • Prominent nucleoli - basophilic.
  • Fibrous septae.
  • Uniform

Image:

IHC

Features:[28]

  • S100 +ve.
  • HMB-45 +ve.
  • Melan A (MART-1) +ve; sometimes -ve.
  • bcl-2 +ve.
  • CD57 +ve (usually).

Keratins:

  • EMA may be +ve.
  • CAM5.2 -ve.
  • AE1/AE3 -ve.

Molecular studies

  • Chromosomal translocation t(12;22)(q13;q12).[28]
    • Fusion transcripts:
      • EWSR1-ATF1.
      • EWSR1-CREB1 (GI tract associated).

Chondrosarcoma

  • May arise from an enchondroma.
  • Usually a good prognosis.

Microscopic

Features:

  • Resembles cartilage at low power.[30]
  • More cellular than cartilage... but relatively paucicellular compared to other sarcomas.

Images:

Grading

Features:[31]

  • Grade I: moderate cellularity +/- binucleated cells.
  • Grade III: nuclear pleomorphism, mitoses common.
  • Grade II: between Grade I and Grade III.

Synovial sarcoma

General

  • Does not arise from cartilage.[32]
  • Young adults or adolescents.

Microscopic

Comes in three flavours:[33][34]

  1. Spindle cell sarcoma with features of hemangiopericytoma, i.e. staghorn vessels.
  2. Biphasic synovial sarcoma:
    1. Spindle cells with features of hemangiopericytoma.
    2. Epitheliod glands or nests.
  3. Primative round cell type.

Images:

IHC

Features:[35]

  • Vimentin +ve + cytokeratin and/or EMA +ve.
  • CD99 +ve.

Others:

Molecular pathology

Unique translocation:

  • t(X;18)(p11.2;q11.2).[38]

See also

References

  1. ↑ WMSP PP.601-3.
  2. ↑ WMSP PP.598-604.
  3. ↑ Skubitz KM, D'Adamo DR (November 2007). "Sarcoma". Mayo Clin. Proc. 82 (11): 1409–32. PMID 17976362. http://www.mayoclinicproceedings.com/content/82/11/1409.long.
  4. ↑ Fletcher CD, Fletcher JA, Dal Cin P, Ladanyi M, Woodruff JM (July 2001). "Diagnostic gold standard for soft tissue tumours: morphology or molecular genetics?". Histopathology 39 (1): 100–3. PMID 11454050.
  5. ↑ URL: http://emedicine.medscape.com/article/1177266-overview. Accessed on: 3 May 2010.
  6. ↑ URL: http://emedicine.medscape.com/article/1178283-overview. Accessed on: 3 May 2010.
  7. ↑ WMSP P.605.
  8. ↑ Ahmed SA, Schuller I (December 2008). "Pediatric hibernoma: a case review". J. Pediatr. Hematol. Oncol. 30 (12): 900–1. doi:10.1097/MPH.0b013e318184e6dd. PMID 19131775.
  9. ↑ Chen DY, Wang CM, Chan HL (March 1998). "Hibernoma. Case report and literature review". Dermatol Surg 24 (3): 393–5. PMID 9537018.
  10. ↑ http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675(06)70271-6
  11. ↑ http://surgpathcriteria.stanford.edu/softfat/hibernoma/
  12. ↑ 12.0 12.1 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 609. ISBN 978-0781765275.
  13. ↑ URL: http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675%2806%2970528-9. Accessed on: 25 June 2010.
  14. ↑ URL: http://wjso.com/content/6/1/86. Accessed on: 25 June 2010.
  15. ↑ URL: http://emedicine.medscape.com/article/1255879-overview. Accessed on: 2 May 2010.
  16. ↑ URL: http://emedicine.medscape.com/article/1255879-overview. Accessed on: 2 May 2010.
  17. ↑ URL: http://emedicine.medscape.com/article/1255879-diagnosis. Accessed on: 2 May 2010.
  18. ↑ URL: http://emedicine.medscape.com/article/1255879-overview. Accessed on: 2 May 2010.
  19. ↑ URL: http://emedicine.medscape.com/article/1255879-diagnosis. Accessed on: 2 May 2010.
  20. ↑ 20.0 20.1 Enzinger & Weiss's Soft Tissue Tumors. 4th Ed. PP.1007-13. ISBN 0-323-01200-0.
  21. ↑ WMSP P.609.
  22. ↑ PMID 18271804.
  23. ↑ PMID 18544056.
  24. ↑ URL: http://www.histopathology-india.net/KS.htm. Accessed on: 31 January 2010.
  25. ↑ Klatt. AOP P.23.
  26. ↑ 26.0 26.1 del Rosario AD, Bui HX, Singh J, Ginsburg R, Ross JS (December 1994). "Intracytoplasmic eosinophilic hyaline globules in cartilaginous neoplasms: a surgical, pathological, ultrastructural, and electron probe x-ray microanalytic study". Hum. Pathol. 25 (12): 1283–9. PMID 7528163.
  27. ↑ Klatt. AOP P.23.
  28. ↑ 28.0 28.1 28.2 28.3 Hisaoka M, Ishida T, Kuo TT, et al. (March 2008). "Clear cell sarcoma of soft tissue: a clinicopathologic, immunohistochemical, and molecular analysis of 33 cases". Am. J. Surg. Pathol. 32 (3): 452–60. doi:10.1097/PAS.0b013e31814b18fb. PMID 18300804.
  29. ↑ URL: http://www.informaworld.com/smpp/723576818-750600/ftinterface~db=all~content=a789166263~fulltext=713240928. Accessed on: 5 May 2010.
  30. ↑ Klatt. AOP P.417.
  31. ↑ WMSP P.643.
  32. ↑ WMSP P.627.
  33. ↑ WMSP P.627.
  34. ↑ Schaal CH, Navarro FC, Moraes Neto FA (2004). "Primary renal sarcoma with morphologic and immunohistochemical aspects compatible with synovial sarcoma". Int Braz J Urol 30 (3): 210–3. PMID 15689250. http://www.brazjurol.com.br/may_june_2004/Schaal_ing_210_213.htm.
  35. ↑ WMSP P.627.
  36. ↑ 36.0 36.1 Horvai AE, Kramer MJ, O'Donnell R (June 2006). "Beta-catenin nuclear expression correlates with cyclin D1 expression in primary and metastatic synovial sarcoma: a tissue microarray study". Arch. Pathol. Lab. Med. 130 (6): 792–8. PMID 16740029.
  37. ↑ Ng TL, Gown AM, Barry TS, et al. (January 2005). "Nuclear beta-catenin in mesenchymal tumors". Mod. Pathol. 18 (1): 68–74. doi:10.1038/modpathol.3800272. PMID 15375433.
  38. ↑ URL: http://www.ncbi.nlm.nih.gov/omim/300813. Accessed on: 30 May 2010.
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