Keywords

1 Definition

  • A rare malignant intraosseous neoplasm composed of spindle cells showing smooth muscle differentiation and devoid of matrix production.

2 Etiology

  • Mostly unknown.

  • Some cases secondary to radiation therapy or associated with Epstein-Barr virus (EBV) infection have been reported.

3 Epidemiology

  • Slight male predominance.

  • More common in adults.

4 Sites of Involvement

  • Most cases occur in long bones, especially the distal metaphysis of the femur and the proximal metaphysis of the tibia.

  • Craniofacial bones and the spine are other reported sites of occurrence.

5 Clinical Symptoms and Signs

  • Pain is the most frequent first symptom.

  • Pathological fracture may occur.

6 Imaging Features

6.1 Radiographic Features

  • Radiographs show a purely osteolytic mass centered in the medullary cavity, with ill-defined margins. Cortical permeation and periosteal reaction suggestive of an aggressive lesion may be seen.

6.2 CT and MRI Features

  • CT and MRI disclose an unusual high preference for this neoplasia to grow much more in length rather than a mediolateral expansion.

  • MR images of the tumor are isointense or hypointense relative to muscle on T1-weighted images. T2-weighted SE images show areas isointense or hypointense relative to fat.

7 Imaging Differential Diagnosis

7.1 Lymphoma of Bone

  • May present similar imaging features.

7.2 Other Malignancies

  • Other primary and secondary malignancies with lytic but otherwise nonspecific images may be considered in individual cases.

8 Pathology

8.1 Gross Features

  • The cut surface of the tumor is fleshy and gray or pinkish white, with areas of necrosis (Fig. 43.1).

  • Margins may be well-defined or poorly defined.

Fig. 43.1
figure 1

Leiomyosarcoma of the metaphysis and diaphysis of a femur, shown in specimen photography and radiography. The lesion involved metallic implants from a previous surgical procedure. (a) Whitish-pink, firm and elastic lesion occupying the marrow space in a mostly longitudinal fashion, permeating the cortex and involving adjacent soft tissue. (b) Absence of mineral deposits in tumor tissue

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8.2 Histological Features

  • Long and interwoven bundles of spindle cells with eosinophilic cytoplasm and characteristic blunt-ended nuclei, with variable pleomorphism, similar to its soft-tissue counterpart (Figs. 43.2 and 43.3). “Schoolfish” pattern.

  • Osteoid is always absent.

  • Epithelioid, myxoid, and pleomorphic variants have been reported.

Fig. 43.2
figure 2

Low-power microscopic view. Long and interwoven bundles of spindle cells

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Fig. 43.3
figure 3

High-power microscopic view. Spindle cells with hyperchromatic nuclei, sometimes showing blunt ends. Atypical mitoses are frequent

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9 Pathologic Differential Diagnosis

  • Metastasis from primary leiomyosarcoma from other sites (especially the uterus and bowel) must be ruled out.

10 Ancillary Techniques

  • Immunohistochemical techniques demonstrate positivity for muscle markers: desmin, h-caldesmon, and smooth muscle actin (SMA) (Figs. 43.4 and 43.5).

Fig. 43.4
figure 4

Medium-power microscopic view of a leiomyosarcoma of a higher grade than the previous figure. Immunohistochemistry may be needed to properly identify the neoplasia

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Fig. 43.5
figure 5

Immunohistochemistry: SMA positive in neoplastic cells

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10.1 Genetics

  • Genomic losses and absence of phosphorylated RB, similar to soft-tissue leiomyosarcoma.

11 Prognosis

  • Histologic grade correlates directly with rates of recurrence and metastasis.

  • Metastasis at diagnosis and less than wide resection with free margins are adverse prognostic factors.

  • Prognosis is statistically better than for other primary bone sarcomas of the same grade in patients without metastasis.

12 Treatment

  • Surgical resection with wide margins combined with chemotherapy is the treatment of choice.