Mesothelioma Diagnosis Differential Diagnosis 1 — Questions and Answers
Question 1: Which malignancy most commonly mimics pleural mesothelioma on imaging and requires IHC for differentiation?
- Metastatic lung adenocarcinoma (Correct answer)
- Primary lung squamous cell carcinoma
- Pulmonary carcinoid
- Primary pleural lymphoma
Correct answer: Metastatic lung adenocarcinoma
Metastatic lung adenocarcinoma to the pleura can produce diffuse pleural thickening identical to mesothelioma on imaging, requiring IHC to differentiate.
Question 2: Which IHC profile helps distinguish pleural mesothelioma (positive) from metastatic adenocarcinoma (negative)?
- Calretinin positive, CEA negative (Correct answer)
- TTF-1 positive, calretinin negative
- CEA positive, WT1 negative
- MOC-31 positive, D2-40 negative
Correct answer: Calretinin positive, CEA negative
Mesothelioma characteristically stains positive for calretinin and negative for CEA, while the reverse pattern is seen in metastatic adenocarcinoma.
Question 3: Reactive mesothelial hyperplasia must be distinguished from mesothelioma because:
- It is benign and does not require cancer treatment (Correct answer)
- It has worse prognosis than mesothelioma
- It always progresses to mesothelioma
- It cannot be sampled by biopsy
Correct answer: It is benign and does not require cancer treatment
Reactive mesothelial hyperplasia is a benign response to pleural injury and infection; misdiagnosing it as mesothelioma would lead to unnecessary aggressive treatment.
Question 4: Which condition most commonly causes benign pleural thickening that mimics mesothelioma on imaging?
- Fibrothorax from prior empyema or hemothorax (Correct answer)
- Pulmonary embolism
- Spontaneous pneumothorax
- Pulmonary sarcoidosis
Correct answer: Fibrothorax from prior empyema or hemothorax
Fibrothorax resulting from prior infection, hemorrhage, or trauma causes benign pleural fibrosis that can radiologically resemble malignant pleural disease.
Question 5: Solitary fibrous tumor of the pleura (SFTP) is distinguished from mesothelioma by which key feature?
- It is usually localized and has a pedunculated attachment to the pleura (Correct answer)
- It is always malignant
- It is diffuse and bilateral
- It always occurs in asbestos-exposed workers
Correct answer: It is usually localized and has a pedunculated attachment to the pleura
SFTP is typically a well-circumscribed, pedunculated, localized mass attached to the pleura by a stalk, in contrast to the diffuse pleural involvement of mesothelioma.
Question 6: Which IHC marker strongly supports synovial sarcoma over sarcomatoid mesothelioma in a chest wall/pleural spindle cell tumor?
- TLE1 positivity with SYT-SSX fusion on FISH (Correct answer)
- Pancytokeratin positivity alone
- D2-40 positivity
- BAP1 loss
Correct answer: TLE1 positivity with SYT-SSX fusion on FISH
TLE1 is a sensitive marker for synovial sarcoma, and the SYT-SSX translocation confirmed by FISH definitively distinguishes it from sarcomatoid mesothelioma.
Mesothelioma Diagnosis Differential Diagnosis 1
Which malignancy most commonly mimics pleural mesothelioma on imaging and requires IHC for differentiation?