Sialoblastomas With Solid Pattern Have FGFR2 Mutations and an Unfavorable Prognosis

Area of Science:

• Oncology
• Pathology
• Genetics

Background:

• Sialoblastoma (SBL) is a rare salivary gland anlage neoplasm with controversial histology, genetics, and behavior.
• The 2022 World Health Organization (WHO) Classification defines SBL as a low-grade malignant tumor.

Purpose of the Study:

• To conduct the first comprehensive clinical, histologic, and molecular analyses of SBLs.
• To better understand the pathogenesis and prognosis of sialoblastoma.

Main Methods:

• Clinical, histologic, and molecular analyses of 8 SBL cases.
• Stratification of tumors into solid and non-solid patterns.
• Genetic profiling including mutation analysis (FGFR2, PALB2, AR, MAP2K1, HRAS) and beta-catenin assessment.

Main Results:

• Solid SBLs (5/8) showed primitive basaloid cells, necrosis, and FGFR2 mutations; all recurred, with 3 developing distant metastases and 2 deaths.
• Non-solid SBLs (3/8) exhibited epithelial-myoepithelial carcinoma (EMC)-like or basal cell adenoma (BCA)-like histology, with HRAS mutations or beta-catenin positivity; none recurred.
• Solid SBLs demonstrated a significantly poorer prognosis compared to non-solid SBLs.

Conclusions:

• Sialoblastomas can be stratified into solid and non-solid patterns, with distinct clinical behaviors and genetic profiles.
• Solid SBLs, frequently harboring FGFR2 mutations, are associated with increased risk of recurrence and metastasis.
• Genetic and morphologic profiling are crucial for predicting SBL prognosis, guiding clinical management.