Mixed Tumor



Mixed Tumor











Panoramic view of a benign mixed tumor. Note the central location, as the tumor is growing just beneath the bronchial mucosa.






Benign mixed tumor is seen with a mixture of epithelial elements image and mesenchymal elements image.


TERMINOLOGY


Abbreviations



  • Mixed tumor (MT)


Synonyms



  • Pleomorphic adenoma (PA)


Definitions



  • Biphasic neoplasm with epithelial/myoepithelial and mesenchymal differentiation


CLINICAL ISSUES


Presentation



  • Cough


  • Incidental finding


  • Hemoptysis


Treatment



  • Surgical approaches



    • Lobectomy


Prognosis



  • Excellent for benign tumor


  • Malignant mixed tumors may need additional therapy


MACROSCOPIC FEATURES


General Features



  • Endobronchial tumor


Size



  • 1-5 cm in greatest dimension


MICROSCOPIC PATHOLOGY


Histologic Features



  • Presence of chondromyxoid background with focal cartilage admixed with epithelial component


Predominant Pattern/Injury Type



  • Biphasic


Predominant Cell/Compartment Type



  • Epithelial, biphasic, or mixed


DIFFERENTIAL DIAGNOSIS


Non-Small Cell Carcinoma



  • In small biopsy with only well-differentiated epithelial component sampled



    • In resected specimens, diagnosis should not pose a problem


Epi-myoepithelial Carcinoma



  • Both tumors show myoepithelial component


  • Epithelial myoepithelial carcinoma does not show presence of cartilage or other heterologous elements


  • Glandular component of inner layer of epithelial cells and outer layer of myoepithelial cells is characteristic of epithelial-myoepithelial carcinoma


Mucoepidermoid Carcinoma



  • Issue in small biopsy with only epithelial component sampled


  • In resected specimens, diagnosis is not a problem


  • Mucoepidermoid carcinomas show presence of mucus-producing and intermediate cells


Carcinosarcoma



  • Carcinosarcomas will show presence of malignant mesenchymal and malignant epithelial components



Pulmonary Hamartoma



  • Most hamartomas will show prominent cartilaginous component and invaginations of epithelium


  • Hamartomas do not show presence of myoepithelial cellular proliferation


DIAGNOSTIC CHECKLIST


Clinically Relevant Pathologic Features



  • Tissue distribution


Pathologic Interpretation Pearls



  • Presence of epithelial/myoepithelial cells admixed with chondromyxoid or cartilaginous areas


GRADING


Benign Mixed Tumors



  • Components are mature elements without atypical histological features


Malignant Mixed Tumor (Ex-Pleomorphic Adenoma)



  • Malignant mixed tumors will display conventional malignant components either in epithelial or mesenchymal component



SELECTED REFERENCES

1. Kamiyoshihara M et al: Pleomorphic adenoma of the main bronchus in an adult treated using a wedge bronchiectomy. Gen Thorac Cardiovasc Surg. 57(1):43-5, 2009

2. Fitchett J et al: A rare case of primary pleomorphic adenoma in main bronchus. Ann Thorac Surg. 86(3):1025-6, 2008

3. Méjean-Lebreton F et al: [Benign salivary gland-type tumors of the bronchus: expression of high molecular weight cytokeratins.] Ann Pathol. 26(1):30-4, 2006

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Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Mixed Tumor

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