Presentation
Parents noticed a progressively enlarging, painless, facial mass on the right.
Patient Data
There is a homogeneously enhancing, destructive soft tissue mass in the right masticator, submandibular, sublingual, and submental soft tissues. There is bone marrow replacement within the right hemimandible with destruction of the lingual cortex extending from the inferior alveolar canal to the parasymphyseal region. There is also destruction of the buccal cortex at the right angle of the mandible. There is loss of normal fat within the medial to the right inferior alveolar canal, as well as within the right retromolar trigone.
There is invasion of the right submandibular space and submandibular gland. There is involvement of the floor of the mouth with medial displacement of the sublingual gland. There is invasion of the anterior belly of the digastric muscle. The lingual septum, intrinsic muscles of the tongue are displaced to the left. Medially, the mass also extends superior to the level of the hard and soft palate.
Case Discussion
This is a case of desmoid fibromatosis located at the right jaw. Due to the size and overall extent of the mass, it was deemed not resectable. The mass was instead biopsied for pathologic analysis.
Histopathology revealed a relatively uniform presence of elongated spindle cells in background of uniformly distributed collagenous stroma. There were minor areas of edema, myxoid change, and a few foci of microhemorrhages without hemosiderin pigment deposition. The cells had relatively fine chromatin, smooth nuclear membranes, and inconspicuous to small uniform round nucleoli. The cells lacked significant cytologic atypia, hyperchromasia, or pleomorphism. The lesional cells infiltrated skeletal muscle and reactive bone. Mitotic figures were rarely identified. The lesional cells had extensive, strong staining for beta catenin (both nuclear and cytoplasmic) and calponin, and frequent weak blush cytoplasmic staining for CKIT. There was weak focal staining for desmin and sparse intermixed Factor XIIa staining cells. Taken together, these findings were consistent with a desmoid fibromatosis given the presence of low-grade spindle cell proliferation and its morphologic and immunohistochemical phenotypic features. There were no features to suggest findings of a malignant spindle cell neoplasm such as low-grade fibromyxoid sarcoma.
The patient was treated with methotrexate and vinblastine. Overall, the patient did well with treatment and surveillance MRIs have shown a progressive decrease in size of the mass.
Co-authors:
Daniel Gewolb, MD
Travis Bevington, MD
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