Neoplasm Name:Solitary fibrous tumor of the pleura

Synonyms:Benign mesothelioma, fibrous mesothelioma, pleural fibroma

ICD-O code:

Cell of Origin: sub-pleural fibrous connective tissue phenotype cells

WHO Grade(s):

Genetics and Associations:

Demographics (Age, Sex, Incidence):sixth and seventh decades, no sex prevalence, uncommon lesion (<5% of the primary pleural tumors)

Common Locations:pleura, mediastinum, pericardium, lung parenchyma. Some extrathoracic locations: meninges, nose, oral cavity, pharynx, epiglotis, salivary gland, thyroid, breast, kidney, bladder and spinal cord.

Gross Appearance:2/3 in visceral pleura, some arise in the fissure, usually between 5 to 10cm of diameter (up to 39cm), pedunculated, firm, rounded or lobulated, sharply circunscribed by lung parenchyma, cut surfaces are pale and lobulated but may have cysts, focal hemorrhage or necrosis.

Histology:solid spindled cell growth or a scerosing growth.

Special Stains:vimentin positive, CD-34 positive, keratin negative.

Radiology:

Radiographic features of an intrapulmonary lesion:
- completely circumscribed by aerated lung on the frontal and lateral views
- similar appearing margins on frontal and lateral views
- shaggy borders (subpleural peripheral lung mass)
- confined to a single lobe
- forms acute angles with adjacent pleura
- changes position with respiration


Radiographic features of an extrapulmonary lesion:

-incomplete border sign: a sharp inferior border and absence of a superior border.The superior border becomes indistinguishable from soft tissue.

-forms obtuse angles with adjacent pleura

-usually is a vertically oriented, elliptical nodule/mass

-smooth well defined margins because it compresses the surrounding normal lung

-mass that is sharply marginated on one view but poorly but poorly marginated on the orthogonal view

-does not change position with respiration but a pedunculated pleural lesion may change position with varied body orientation (left or right decubitus –vs- supine –vs- prone –vs- upright, etc..

-pleural lesion may extend across fissures

Note: Pedunculated lesion of the pleura can present with radiographic features of both pleural and parenchymal lesions, which can make them even more difficult to define. · At this point the lesion can be characterized as a peripheral, solitary, non-calcifying, homogeneous, smooth, well circumscribed, 6 cm opacity/mass that forms obtuse angles with adjacent pleura and demonstrates an incomplete border sign. Therefore, an extrapulmonary mass is favored at this point, but before a differential diagnosis is constructed one should seek out old radiographs in order to compare with the recent study.



Progression: 12% are malignant and 88% benign but even the benign have a potencial of relapsing and should be followed up for at least 5 years after resection.

Prognosis and Treatment: good prognosis if completely resected. No effective adjuvant treatment with radio or chemotherapy for the malignant form.

COMMENTS:In 80 cases seen by Rosado-de-Christenson et al 54% of the cases did not included solitary fibrous tumor (SFT) as a possible diagnosis; SFT was a possible diagnosis in 26% and a pleural tumor was diagnosed in 20% of the cases.