Table of Contents
Undifferentiated pleomorphic sarcoma (UPS) is a rare but highly aggressive malignant tumor of mesenchymal origin. Formerly termed malignant fibrous histiocytoma, UPS is now recognized as a diagnosis of exclusion, applied only when no specific line of differentiation can be identified despite thorough histopathologic and immunohistochemical evaluation. Although uncommon in the oral and maxillofacial region, its rapid growth and destructive potential make early recognition critical for dental professionals.
Definition and Biological Behavior
UPS is a high-grade sarcoma composed of pleomorphic spindle and polygonal cells without identifiable epithelial, muscular, neural, or vascular differentiation. The tumor is characterized by:
- Marked cellular pleomorphism- High mitotic activity
- Aggressive local invasion
- Early recurrence and potential for distant metastasis
Epidemiology and Etiology
- Rare in the oral cavity and jaws- Predominantly affects middle-aged and older adults
- Slight male predilection
Radiation-associated UPS tends to be particularly aggressive.
Common Oral and Maxillofacial Sites
- Mandible and maxilla- Buccal mucosa
- Tongue
- Paranasal sinuses
- Deep facial soft tissues
Both soft tissue and intraosseous presentations have been documented.
Clinical Presentation
UPS typically presents as:
- A rapidly enlarging mass- Firm, poorly defined swelling
- Pain or tenderness in advanced cases
- Ulceration of overlying mucosa
- Tooth displacement or loosening (jaw involvement)
- Facial asymmetry or paresthesia
Early lesions may mimic benign fibrous or reactive oral lesions, leading to delayed diagnosis.
Pathology
Gross Features
- Poorly circumscribed tumor
- Infiltrative margins
- Gray-white, fleshy cut surface
- Areas of hemorrhage and necrosis
Histopathological Features
Microscopic examination reveals:
- Highly pleomorphic spindle and polygonal cells- Storiform (cartwheel) growth pattern
- Hyperchromatic nuclei
- Numerous atypical mitotic figures
- Multinucleated tumor giant cells
- Areas of necrosis and hemorrhage
- Infiltrative growth into adjacent tissues
No specific differentiation is identifiable.
Immunohistochemistry
Immunohistochemical staining is essential to exclude other malignancies:
- Vimentin: positive- Cytokeratins: negative
- Desmin and SMA: negative
- S100: negative
- CD31/CD34: negative
- High Ki-67 proliferation index
Differential Diagnosis
- Fibrosarcoma
- Leiomyosarcoma
- Rhabdomyosarcoma
- Spindle cell carcinoma
- Angiosarcoma
- Malignant peripheral nerve sheath tumor
UPS is diagnosed only after these entities are excluded.
Imaging Characteristics
Radiographic Features
- Ill-defined radiolucency in jaw lesions- Cortical bone destruction
- Possible tooth root resorption
CT and MRI
- Poorly defined soft tissue mass- Heterogeneous enhancement
- MRI best demonstrates soft tissue invasion
Imaging helps assess tumor extent but is not diagnostic.
Management and Treatment
- UPS requires aggressive multidisciplinary management:
- Wide surgical excision with clear margins (primary treatment)- Adjuvant radiotherapy for:
= High-grade tumors
= Close or positive margins
= Inoperable lesions- Complete excision is often difficult in the head and neck region.
Prognosis
UPS has an overall poor prognosis:
- High local recurrence rate
- Hematogenous metastasis, commonly to the lungs
- Five-year survival approximately 30–60%
- Prognosis worsens with:
= Large tumor size
= Deep tissue invasion
= Positive surgical margins
= Radiation-induced origin
Early diagnosis improves outcomes.
Importance for Dental Professionals
Dental practitioners are often the first clinicians to encounter these lesions. Key responsibilities include:
- Recognizing rapidly enlarging or atypical oral masses- Avoiding assumptions of benignity
- Prompt biopsy and referral
- Long-term follow-up and oral rehabilitation after treatment
Conclusion
Undifferentiated pleomorphic sarcoma is a rare but highly aggressive malignancy of the oral and maxillofacial region. Its nonspecific clinical appearance and complex histopathology demand a high index of suspicion from dental professionals. Early detection, accurate diagnosis, and prompt multidisciplinary treatment are essential to improve patient survival and quality of life.