TUMOR FIBROSO MALIGNO SOLITARIO DE LA PLEURA
England et al5 reviewed 223 cases of localized fibrous tumor of the pleura and developed histologic criteria to separate malignantlesions from their benign counter-parts.Criteria for malignancy include high cellularity, high mitotic rate (more than 4 mitoses per 10high-power fields), pleomorphism,hemorrhage, and necrosis. Our case exhibited malignant histologic features including areas of high cellularity, mitoses,cellular pleomorphism,and focal necrosis.
Histologic differential diagnoses of pleural-based malignant spindle cell tumors include malignant localized fibrous tumor, spindle cell carcinoma,Sarcomatoid malignant mesothelioma, and various sarcomas. Immunohisto-chemical studies are usually helpful in separating these entities.
Localized fibrous tumors of thepleura are negative for keratin and are frequently reactive for CD34.Both spindle cell carcinomas and sarcomatoid malignant mesotheliomas are positive for keratin.Additionally, malignant mesothe-liomas may also be positive for mesothelial marker calretinin.Sarcomas are typically negative for both keratin and CD34, although positive staining for either markermay occur in rare cases.
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