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Soft Tissue Sarcomas Interactive Course - Case 2 Author: André Mascarenhas Oliveira Pathology Resident - Mayo Clinic, Rochester, MN - USA Radiology Comments: Guilherme Baptista Villa Radiology Resident - Universidade Estadual do Rio de Janeiro, Rio de Janeiro, Brazil

Diagnosis: Fibrosarcoma

Until few decades ago, the fibrosarcomas were considered one of the most common soft tissue sarcomas. The recent development and improvement of new diagnostic tools, such as immunohistochemistry and cytogenetics, have contributed to reclassify many of these tumors in other entities like malignant fibrous histiocytoma*, monophasic synovial sarcoma or malignant peripheral nerve sheath tumor (MPNST). Currently, the fibrosarcomas comprise less than 5% of the soft tissue sarcomas1.

The fibrosarcomas can be divided in two groups: the fibrosarcoma of the adult and the congenital fibrosarcoma. Furthermore, other types have been described, like the inflammatory fibrosarcoma, pos-irradiation fibrosarcoma and epithelioid fibrosarcoma. In this short review, we will focus in the adult fibrosarcoma.

Adult Fibrosarcoma

The fibrosarcoma of the adult occurs usually between the forth and sixth decades of life and affects equally both sexes1. At present, these tumors occur more frequently in the inferior extremities (30%), thorax and abdomen (15%), superior extremities (15%) and head and neck (10-15%)1. However, these percentages can vary from different sources and will depend on the accuracy of the diagnosis2,3.

The adult fibrosarcomas are usually slow growing, deep seated and painless tumors. Macroscopically, they are fleshy, white-grayish and moderately well-circumscribed. Histologically, they are composed by spindle-shaped cells that exhibit a characteristic fascicular pattern of growth - the "herringbone" pattern (figures 1, 2, 3 and 4). Mitosis and necrosis are variable and correlate with the histologic grade. Collagen fibers are present in variable amounts and are inversely correlated with the histologic grade3. Extensive calcification can occasionally be present but in these cases, the diagnosis of synovial sarcoma must be considered4.

(click image to zoom) Figure 1. Proliferation of spindle cells in a characteristic herringbone pattern (H&E, 160X). [Slides provided by AG Nascimento, MD. Mayo Clinic, Rochester, MN, USA]

(click image to zoom) Figure 2. Proliferation of spindle cells in a characteristic herringbone pattern (H&E, 160X). [Slides provided by AG Nascimento, MD. Mayo Clinic, Rochester, MN, USA]

(click image to zoom) Figure 3. Increased mitotic activity in a high grade tumor (H&E, 400X). [Slides provided by AG Nascimento, MD. Mayo Clinic, Rochester, MN, USA]

(click image to zoom) Figure 4. Increased mitotic activity in a high grade tumor (H&E, 400X). [Slides provided by AG Nascimento, MD. Mayo Clinic, Rochester, MN, USA]

Radiology

At this time, the magnetic resonance imaging (MRI) is considered the gold standard imaging modality to evaluate soft tissue neoplasms, although other methods such as computed tomography and ultrasonography can be used in the initial work up6,7. However, none of them is accurate enough to make a specific diagnosis.

In the cases of fibrosarcoma, MRI shows a signal intensity close to muscle's on T1 weighted images, a high signal intensity with some low signal areas on T2 weighted images, and not uncommonly, a nonhomogeneous pattern of enhancing after the use of paramagnetic contrast agents8.

Currently, the fibrosarcoma is considered a diagnosis of exclusion and the immunohistochemical analysis must reveal absence staining for cytokeratins, epithelial membrane antigen, desmin and S-100 protein3. The differential diagnosis includes fibromatosis, nodular fasciitis, fibromyxosarcoma, monophasic synovial sarcoma, malignant fibrous histiocytoma, MPNST and sarcomatoid carcinoma.

Radical excision, associated or not with radiotherapy, is the therapy of choice4. Adjuvant chemotherapy has also been used in high grade lesions4. The local recurrence rate ranges between 18 and 79% (mean 42%) according to the type of resection and the adequacy of the surgical margins5. Distant metastases occur in 63% of the cases within 5 years after the diagnosis and the lungs and bones are the most common sites4,5. Currently, the overall 5-year survival rate of the adult fibrosarcoma is 39%5.

*The malignant fibrous histiocytoma is considered another controversial entity and will be discussed in coming reviews.

References

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