Mesothelioma Diagnosis Differential Diagnosis 2 — Questions and Answers
Question 1: Peritoneal mesothelioma must be differentiated from primary peritoneal carcinoma by which IHC finding?
- Calretinin and WT1 positive vs. PAX8 and ER positive in carcinoma (Correct answer)
- CEA positivity in mesothelioma
- CK20 in mesothelioma vs. CK7 in carcinoma
- TTF-1 in mesothelioma
Correct answer: Calretinin and WT1 positive vs. PAX8 and ER positive in carcinoma
Peritoneal mesothelioma stains positive for calretinin and WT1 while primary peritoneal serous carcinoma stains positive for PAX8, ER, and Ber-EP4.
Question 2: Pleural involvement by breast carcinoma can be excluded in favor of mesothelioma by the absence of which markers?
- ER, GATA3, and mammaglobin (Correct answer)
- Calretinin and WT1
- D2-40 and CK5/6
- TTF-1 and Napsin A
Correct answer: ER, GATA3, and mammaglobin
ER, GATA3, and mammaglobin are breast carcinoma markers; their absence, combined with positive mesothelial markers, supports mesothelioma over metastatic breast cancer.
Question 3: Which rare pleural tumor is composed of lipomatous elements and must be distinguished from mesothelioma with lipomatous areas?
- Well-differentiated liposarcoma (Correct answer)
- Epithelioid hemangioendothelioma
- Desmoid tumor
- Pleomorphic carcinoma
Correct answer: Well-differentiated liposarcoma
Well-differentiated liposarcoma of the pleura contains mature fat and atypical lipoblasts, which distinguishes it from any fat-containing mesothelioma variant.
Question 4: Pleural epithelioid hemangioendothelioma (EHE) is distinguished from mesothelioma by positive staining for which marker?
- CD31 and ERG (endothelial markers) (Correct answer)
- Calretinin
- WT1
- D2-40
Correct answer: CD31 and ERG (endothelial markers)
EHE is a vascular tumor that stains for endothelial markers CD31 and ERG, which are absent in mesothelioma.
Question 5: A pleural biopsy showing diffuse large B-cell lymphoma cells would be differentiated from mesothelioma by which finding?
- CD20 positivity and cytokeratin negativity (Correct answer)
- Calretinin positivity
- BAP1 loss
- CDKN2A deletion
Correct answer: CD20 positivity and cytokeratin negativity
DLBCL expresses B-cell marker CD20 and lacks cytokeratin expression, which is the opposite of mesothelioma's keratin-positive, CD20-negative profile.
Question 6: Paraganglioma occurring in the posterior mediastinum may mimic mesothelioma on imaging; it is distinguished by positive staining for:
- Synaptophysin and chromogranin A (Correct answer)
- Calretinin and WT1
- CK5/6 and D2-40
- TTF-1 and Napsin A
Correct answer: Synaptophysin and chromogranin A
Paragangliomas are neuroendocrine tumors that express synaptophysin and chromogranin A, neuroendocrine markers completely absent in mesothelioma.
Mesothelioma Diagnosis Differential Diagnosis 2
Peritoneal mesothelioma must be differentiated from primary peritoneal carcinoma by which IHC finding?