Radiologic Diagnosis

STS of the Extremity and Trunk

Patients who present with very small or superficial tumors do not necessarily require an imaging study, as excisional biopsy and pathologic evaluation may be the most reasonable diagnostic study. Either a CT scan or MRI is appropriate in the evaluation of all other patients with a soft tissue mass of the extremity or trunk. MRI is increasingly utilized however, if cost or availability are not an issue. While both studies are useful in the measurement of tumor size and assessment of depth, several benign tumors have characteristic MRI appearances that may facilitate the correct preoperative diagnosis. These include lipomas, hemangiomas, nerve sheath tumors and myxomas. A soft tissue mass of the extremity that does not appear characteristic of one of the benign tumors listed above, is heterogeneous in appearance, does not involve bone, and displaces surrounding structures is highly suggestive of a


Retroperitoneal Tumors

A CT scan with oral and intravenous contrast is the diagnostic procedure of choice for patients with a retroperitoneal mass. Most patients who present with a retroperitoneal mass will be found to have a malignant tumor, with lymphoma, testicular carcinoma, renal cell carcinoma, and STS in the differential diagnosis. A CT scan can be very useful in determining which of these is the most likely diagnosis. An isolated retroperitoneal mass without evidence of additional central or peripheral adenopathy is unlikely to represent lymphoma. Tumors that arise in the midline in a male patient should be considered testicular carcinoma until proven otherwise (with a negative testicular ultrasound and negative tumor markers). Direct involvement or destruction of the kidney is more likely due to a primary renal cell

Table 4.5. Nonrandom cytogenetic abnormalities in STS

Histologic Subtype

Cytogenetic Abnormality

Synovial sarcoma

Alveolar rhabdomyosarcoma

Ewing's sarcoma

Myxoid liposarcoma

Extraskeletal myxoid chondrosarcoma t(X;18)(p11.2;q11.2) t(2;13)(q35-37;q14) t(11;22)(q21-24;q11-14) t(12;16)(q13;p11) t(9;22)(q22;q11-12)

MPNT=malignant peripheral nerve sheath tumor

carcinoma than a STS, which more commonly displaces the kidney and its vasculature.

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