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Review
. 2023 Mar;17(1):259-264.
doi: 10.1007/s12105-022-01479-w. Epub 2022 Sep 28.

Biphenotypic Sinonasal Sarcoma with a Novel PAX3::FOXO6 Fusion: A Case Report and Review of the Literature

Meredith M Nichols  1 , Fatimah Alruwaii  1 , Mohamad Chaaban  2 , Yu-Wei Cheng  3 , Christopher C Griffith  4
Affiliations
Review

Biphenotypic Sinonasal Sarcoma with a Novel PAX3::FOXO6 Fusion: A Case Report and Review of the Literature

Meredith M Nichols et al. Head Neck Pathol. 2023 Mar.

Abstract

Background: Biphenotypic sinonasal sarcoma (BSS) is a low-grade, locally aggressive sarcoma unique to the sinonasal region. BSS is most common in middle aged patients and affects women more frequently than men. It is characterized by a bland spindled cell proliferation with neural and myogenic differentiation. BSS are usually associated with rearrangement t(2;4)(q35;q31.1) resulting in a PAX3::MAML3 fusion. Less commonly, other genes are found in combination with PAX3 and some cases reported in the literature have an unknown fusion partner.

Methods: A 54-year-old man presented with nasal mass. Endoscopic resection showed a low-grade spindle cell neoplasm with morphologic features of BSS and immunohistochemical and next generation sequencing were performed to confirm the diagnosis.

Results: The tumor was positive for S100 and smooth muscle actin but negative for SOX10. Next generation sequencing demonstrated a novel PAX3::FOXO6 gene fusion.

Conclusions: Although a PAX3::FOXO6 gene fusion has never been reported, this finding combined with the morphologic and immunophenotypic features supports the diagnosis of supports the diagnosis of BSS.

Keywords: Biphenotypic sinonasal sarcoma; PAX3:FOXO6; TRK.

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Conflict of interest statement

The authors have no conflicts of interest.

Figures

Fig. 1
Fig. 1
Pre-operative imaging findings. A CT without contrast demonstrated a mucosal mass adherent to the right middle turbinate (arrow). B MRI with contrast showed the mass extended into the sphenoid sinus with involvement of the right posterior ethmoid air cells, possibly compatible with an inverted sinonasal papilloma (arrow)
Fig. 2
Fig. 2
Histologic features. A Histologic examination showed a spindle cell neoplasm with sharply demarcated areas of myxoid to collagenous background. B & C The more cellular areas showed the characteristic fascicular and herringbone arrangement of uniform plump cells with cleared cytoplasm, prominent borders and wavy to elongated euchromatic nuclei with no cytologic atypia. D Infiltrative growth was evident microscopically with entrapment of submucosal glands (not shown) and pre-existing bony trabeculae
Fig. 3
Fig. 3
Immunohistochemical stains. A typical cellular area of the tumor on a hematoxylin and eosin stained section (A). Neoplastic cells were focally positive for S100 (B) and smooth muscle actin (C). Pan-TRK showed increased cytoplasmic expression (D)
Fig. 4
Fig. 4
NGS read alignment to the reference genome (Hg19) shows the identified PAX3::FOXO6 fusion product. The PAX3 exon 7 matched perfectly to the reference, while the FOXO6 exon 2 (shown in the blue rectangle) mis-aligned to the PAX3 intron 7 sequence. Noticed that the PAX3 sequence is shown on the positive DNA strand
See this image and copyright information in PMC

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