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  • Leiomyosarcoma (LMS) is an aggressive sarcoma thought to arise from the smooth muscle cells lining small blood vessels
    • it may either occur in the soft tissue (uterus) or in the bone  
  • Epidemiology
    • incidence
      • fewer than 100 case reports of extra-facial leiomyosarcoma of bone
    • demographics
      • the mean age of presentation is in 5th and 6th decades of life
    • location
      •  most frequently occurs in the metaphysis of long bones, but can occur in diaphyseal locations.
      • the most frequent sites of boney presentation are the femur, tibia, ilium, and humerus
  • Prognosis
    • LMS of bone in adults
      • 25% recurrence rate and 25% metastasis rate 
      • 75% survival at 3 years with treatment
  • Symptoms
    • bone pain
    • palpable mass 
    • typical duration of symptoms prior to diagnosis is 6 months 
  • Physical exam
    • pelvic masses can be difficult to appreciate on inspection exam
    • can be tender or nontender to palpation
    • masses will be firm
  • Radiographs
    • involved extremity  
      • purely osteolytic lesions with ill-distinct margins, moth-eaten, or permeative pattern of bone destruction.  
      • primarily intra-medullary but may extend into the soft tissues.  
    • chest 
      • indicated for all staging of tumors to evaluate for lung metastasis
  • CT
    • indications
      • help evaluate bone loss of involved extremity or pelvis
      • chest CT indicated in all patients as part of staging workup to evaluate for metastasis
  • MRI
    • indications
      • differentiate from benign soft tissue tumors
      • evaluate size, depth, and surrounding anatomy
    • views
      • appears dark on T1, similar to muscle tissue 
      • appears heterogeneous on T2 with areas of increased signal intensity 
      • contrast causes diffuse enhancement of signal within the lesion
  • Histology
    • a spindle cell neoplasm with similar characteristics shared between the osseous and soft tissue forms of this disease 
    • cigar-shaped nuclei
    • cells arranged into fascicles along with myofibrils running parallel 
    • presence of actin and vimentin immunoreactivity  
  • Staging
    • all tumors should be staged appropriately prior to treatment initiation
  • Nonoperative
    • chemotherapy
      • indications
        • diffuse metastatic disease to the lungs
        • large pelvic masses with neurovascular involvement that preclude safe resection
      • outcomes
        • variable response to chemotherapy
        • better survival when chemotherapy combined with surgery than surgery alone
    • radiation
      • indications
        • controversial 
        • contaminated resection bed
      • outcomes
        • variable response, difficult to predict
  • Operative
    • early wide resection of the primary lesion and secondary reconstruction
      • indications
        • standard of care in localized disease
      • technique
        • clean margin is an important goal of surgical resection
      • chemotherapy
        • Neo-adjuvant or adjuvant  chemo/radiotherapy in the treatment of leiomyosarcoma of bone is controversial
      • radiation
        • if unable to obtain wide margin consider adjuvant radiation

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Questions (1)

(OBQ08.8) A 35-year-old female presents to your office after incidental finding of a aggressive looking lytic lesion in her pelvis. She has no pain, is not pregnant, but states she has been losing weight over the last 6 months for an unknown reason. Bone scan shows significant uptake in the area of her pelvis. Immunohistochemistry stains positive for smooth muscle actin. Which of the following slides correlates to your expected findings on histology? Review Topic


Figure A




Figure B




Figure C




Figure D




Figure E



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Based on the patients history (unexplained weight loss) and bone scan, she has an aggressive lesion in her pelvis. Immunohistochemisty staining for smooth muscle actin suggests a tumor of smooth muscle origin - or a leiomyosarcoma. The prefix - "leio-" designates smooth muscle tumors. The histopathology presented in Figure A shows interlacing bundles of smooth muscle cells with variable uniformity, high nuclear/cytoplasmic ratio, and mitotic figures - consistent with leiomyosarcoma.

The two cited review articles by Berlin et al and Antonescu et al describe the clinical, radiographic, and histology of this disease as described above.

Incorrect Answers:
Figure B - Giant cell tumor
Figure C - Myeloma
Figure D - Osteosarcoma
Figure E - hyaline cartilage

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