ย Case Summary
Patient: 52-year-old female
Chief Complaints: Chronic ear discharge since childhood, gradually progressive hearing loss, and occasional nasal blockage.
History: The patient was advised ear surgery following evaluation for chronic otitis media. She underwent cortical mastoidectomy with tympanoplasty, with subsequent improvement in hearing.
Preoperative Work-up:
HRCT temporal bone: Mastoid sclerosis
Pure tone audiometry (PTA): Moderate mixed hearing loss
Tympanometry: Type B curve
Laboratory: Anemia, borderline blood sugar (medically managed).Routine test for pre anaesthetic checkup.
IntraOperative and Pathological Findings
Specimen: Biopsy from mastoid antrum showing fleshy polypoid soft tissue and bone dust.
Microscopy (Drs. Tribedi & Roy Diagnostic Laboratory):
Spindle cell proliferation composed of ovoid to spindle-shaped vesicular nuclei and pale cytoplasm.
No pleomorphism, mitosis, or necrosis.
Impression: Spindle cell neoplasm โ immunohistochemistry advised.
IHC and Final Diagnosis (Centre for Oncopathology, Tata Trusts):
Positive markers: S100, SMA, PAN-TRK
Negative markers: SOX10, Desmin, CD34, Pan-cytokeratin
MIB-1 index: Very low
Diagnosis: Biphenotypic Sinonasal Sarcoma (BSNS)
Low-grade sarcoma showing dual neural and myogenic differentiation, associated with PAX3 translocation.
Rarely arises in the middle ear, typically seen in sinonasal tract.
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Discussion
Biphenotypic Sinonasal Sarcoma is a rare, low-grade spindle cell sarcoma showing dual differentiation โ neural (S100, SOX10) and myogenic (SMA, calponin). It is characteristically driven by a PAX3โMAML3 gene fusion.
Middle Ear Involvement
Exceptionally uncommon; only isolated case reports exist.
Likely arises from pluripotent mesenchymal cells in the middle ear mucosa or through secondary extension.
Clinical presentation overlaps with chronic ear disease, leading to diagnostic delay.
Differential Diagnosis
Differential Key Distinguishing Feature
Schwannoma S100+, SOX10+, lacks SMA
Leiomyosarcoma SMA+, Desmin+, lacks neural markers
Sarcomatoid carcinoma Cytokeratin+
Synovial sarcoma SS18โSSX fusion, Cytokeratin+
BSNS PAX3 fusion, neural + myogenic markers
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Management
Complete surgical excision is the mainstay.
Adjuvant radiotherapy may be indicated for positive margins.
Chemotherapy: Limited benefit due to low-grade behavior.
Follow-up: Long-term surveillance essential due to local recurrence risk (~30โ40%).
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Key Learning Points
๐งฉ 1. BSNS may rarely arise in or extend to the middle ear, mimicking chronic ear disease.
๐งฌ 2. Accurate diagnosis requires IHC and molecular confirmation (PAX3 fusion).
โ๏ธ 3. Low-grade but locally aggressive, demanding wide excision and long follow-up.
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References (PubMed-linked)
1. Lewis JT et al. Am J Surg Pathol. 2012;36(10):1479โ1492.
2. Bishop JA. Head Neck Pathol. 2017;11(4):472โ477.
3. Tahara M et al. Hum Pathol. 2019;84:276โ282.
4. WHO Classification of Head and Neck Tumours, 5th Edition, 2022.
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