Keywords

Definition

  • A rare malignant intraosseous neoplasm, constituted by spindle cells showing smooth muscle differentiation and devoid of matrix production

Etiology

  • Mostly unknown.

  • Some cases secondary to radiation therapy or associated to EBV infection were reported.

Epidemiology

Sex

  • There is a slight male predominance.

Age

  • More common in adults

Sites of Involvement

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

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

Clinical Symptoms and Signs

  • Pain is the most frequent first symptom.

  • Pathological fracture may occur.

Image Diagnosis

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.

CT and MRI Features

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

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

Imaging Differential Diagnosis

Lymphoma of Bone

  • May present similar imaging features

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

Pathology

Gross Features

  • The cut surface of the tumor is fleshy and gray pinkish white, with areas of necrosis, with well or poorly defined margins.

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.

  • Osteoid is always absent.

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

Pathology Differential Diagnosis

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

Ancillary Techniques

  • Immunohistochemical techniques demonstrate positivity for muscle markers: desmin, h-caldesmon, and smooth muscle actin.

Genetics

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

Prognosis

  • Histologic grade correlates directly with recurrence and metastatic rates.

  • Prognosis may be better than for other primary bone sarcomas of the same grade in nonmetastatic patients.

Treatment

  • Surgical resection and chemotherapy

Images

See Figs. 40.1, 40.2, 40.3, 40.4, and 40.5 for illustrations of leiomyosarcoma of the bone.

Fig. 40.1
figure 1

Leiomyosarcoma of the metaphysis and diaphysis of a femur. 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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Fig. 40.2
figure 2

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

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Fig. 40.3
figure 3

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

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Fig. 40.4
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. 40.5
figure 5

Immunohistochemistry – SMA positive in neoplastic cells

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