Head and Neck Soft Tissue Pathology
Core Concepts
Soft tissue lesions of the head and neck span reactive, benign, and malignant entities. Know nodular fasciitis, fibromatosis, myofibroma, lipoma variants, schwannoma, neurofibroma, hemangioma, vascular malformations, and sarcomas (synovial sarcoma, rhabdomyosarcoma, angiosarcoma). Understand the role of IHC: SMA, desmin, S100, CD34, and cytokeratins. Recognize that many soft tissue lesions in children are benign and that site and age narrow the differential.
Common Traps
- Misdiagnosing nodular fasciitis as sarcoma because of rapid growth and mitoses; it is self-limited and lacks atypical mitoses.
- Missing synovial sarcoma in a young adult with a head and neck mass; it is cytokeratin and TLE1 positive.
- Confusing fibromatosis with a low-grade sarcoma; fibromatosis is infiltrative but lacks atypia.
- Overlooking angiosarcoma in a violaceous scalp lesion in an older adult.
Rule of Thumb
Use a site-age-morphology triad. A worked example: a rapidly growing 2-cm forearm-like lesion in the neck of a young adult shows plump fibroblasts in a myxoid stroma with extravasated red cells and mitoses - diagnose nodular fasciitis and avoid overtreatment; confirm with SMA positivity and lack of atypical mitoses. In contrast, a deep mass with spindle cells and cytokeratin positivity in a young adult suggests synovial sarcoma.
Ancillary Testing
Order a targeted IHC panel rather than a broad screen; document margin status for sarcomas.