Expanding the clinicopathological spectrum of TGFBR3-PLAG1 rearranged salivary gland neoplasms with myoepithelial differentiation including evidence of high-grade transformation

Genes Chromosomes Cancer. 2022 Feb;61(2):94-104. doi: 10.1002/gcc.23009. Epub 2021 Nov 17.


PLAG1 rearrangements have been described as a molecular hallmark of salivary gland pleomorphic adenoma (PA), carcinoma ex pleomorphic adenoma (CEPA), and myoepithelial carcinoma (MECA). Several fusion partners have been described, however, commonly no further assignment to the aforementioned entities or a morphological prediction can be made based on the knowledge of the fusion partner alone. In contrast, TGFBR3-PLAG1 fusion has been specifically described and characterized as an oncogenic driver in MECA, and less common in MECA ex PA. Here, we describe the clinicopathological features of three TGFBR3-PLAG1 fusion-positive salivary gland neoplasms, all of which arose in the deep lobe of the parotid gland. Histopathology showed high morphological similarities, encompassing encapsulation, a polylobular growth pattern, bland basaloid and oncocytoid cells with myoepithelial differentiation, and a distinct sclerotic background. All cases showed at least limited, unusual foci of minimal invasion into adjacent salivary gland tissue, including one case with ERBB2 (Her2/neu) amplified, TP53 mutated high-grade transformation, and lymph node metastases. Of note, all cases illustrated focal ductal differentiation. Classification remains difficult, as morphological overlaps between myoepithelial-rich cellular PA, myoepithelioma, and MECA were observed. However, evidence of minimal invasion advocates classification as low-grade MECA. This case series further characterizes the spectrum of uncommon cellular myoepithelial neoplasms harboring TGFBR3-PLAG1 fusion, which show recurrent minimal invasion of the adjacent salivary gland tissue, a predilection to the deep lobe of the parotid gland, and potential high-grade transformation.

Keywords: adenoma; parotid gland; pleomorphic; salivary gland neoplasms; transforming growth factor beta.

Publication types

  • Case Reports

MeSH terms

  • Adenoma, Pleomorphic* / diagnosis
  • Adenoma, Pleomorphic* / diagnostic imaging
  • Adenoma, Pleomorphic* / genetics
  • Adenoma, Pleomorphic* / pathology
  • Adult
  • Aged
  • DNA-Binding Proteins / genetics*
  • Gene Rearrangement / genetics*
  • Humans
  • Male
  • Neoplasm Grading
  • Oncogene Proteins, Fusion / genetics*
  • Parotid Gland / diagnostic imaging
  • Parotid Gland / pathology
  • Proteoglycans / genetics*
  • Receptors, Transforming Growth Factor beta / genetics*
  • Salivary Gland Neoplasms* / diagnosis
  • Salivary Gland Neoplasms* / diagnostic imaging
  • Salivary Gland Neoplasms* / genetics
  • Salivary Gland Neoplasms* / pathology
  • Transforming Growth Factor beta / metabolism


  • DNA-Binding Proteins
  • Oncogene Proteins, Fusion
  • PLAG1 protein, human
  • Proteoglycans
  • Receptors, Transforming Growth Factor beta
  • Transforming Growth Factor beta
  • betaglycan

Supplementary concepts

  • Salivary Gland Adenoma, Pleomorphic