IS case 484: Aggressive fibromatosis/desmoid tumor
Imaging Sciences URMC 2010
Publication Date: 2010-08-30
Initial chest x-ray demonstrated a large soft tissue mass in the posterior aspect of the left lung base. Subsequent CT images demonstrated the mass projecting into the left lower lobe with small atelectasis; mass abutted the ribs posteriorly, the spine and posterior mediastinum medially, and the diaphragm inferiorly. There was minimal involvement of surrounding structures. PET was performed (not shown) and demonstrated only mild irregular FDG uptake, with lesion measuring approximately 1.8 SUV. Needle biopsy confirmed myxoid spindle cell lesion consistent with aggressive fibromatosis/desmoid tumor. Following en bloc resection, focal invasion of the intercostal muscles and the 10th rib was noted, in addition to diffuse chronic inflammatory changes in the local soft tissues, including the diaphragm. No tissue necrosis or evidence of malignancy was identified.
Desmoid tumors, more formally referred to as fibromatoses, are monoclonal proliferations of bland, nonmalignant fibroblastic cells which are classically described as locally aggressive but benign lesions. Desmoids may grow to significant size and are usually over 5 cm in diameter at time of diagnosis. More aggressive forms may demonstrate evidence of local invasion of surrounding soft tissues. Due to the size of the lesions and associated symptoms, standard of care is surgical resection with wide margins. Radiotherapy is reserved for inoperable lesions and for resection margins with residual tumor. Recurrence is common.
Imaging findings are highly variable; in MRI, lesion assumes signal characteristics of both fat and skeletal muscle with heterogeneous contrast enhancement, although at least 10% of lesions do not enhance. CT demonstrates a nonspecific soft tissue mass with often indistinct margins which may be hypodense, isodense, or hyperdense to muscle. Desmoid tumors are more common in women, occur in up to 20% of people with Gardner's syndrome, and may arise within the abdomen (intra-abdominal desmoid), abdominal wall (abdominal desmoid), or thoracic wall/cavity (extra-abdominal desmoid).
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