A 58-year-old male smoker has a rapidly enlarging parotid mass with facial weakness. Histology shows high-grade carcinoma composed of large pleomorphic cells forming duct-like structures, resembling invasive ductal carcinoma of the breast. Immunohistochemistry is most likely to show positivity for:
- A Androgen receptor ✓
- B CD20
- C Chromogranin A
- D S100 protein diffusely
Correct answer: A. Androgen receptor
Explanation
Salivary duct carcinoma is an aggressive high-grade malignancy histologically mimicking breast ductal carcinoma, with comedo necrosis and duct formation. It characteristically expresses androgen receptor, which is diagnostically useful and therapeutically relevant since androgen deprivation has been tried in advanced disease. Many cases also show HER2 amplification. CD20 marks lymphoma, chromogranin marks neuroendocrine tumours, and diffuse S100 positivity suggests acinic cell carcinoma or neural differentiation, none of which fit this morphology.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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