Lung
Mesenchymal tumors
Solitary fibrous tumor
Author: Roseann Wu, M.D., M.P.H.
Topic Completed: 1 January 2016
Minor changes: 17 March 2021
Copyright: 2003-2021, PathologyOutlines.com, Inc.
PubMed Search: Solitary fibrous tumor [title] lung
Table of Contents
Definition / general | Essential features | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Radiology description | Radiology images | Prognostic factors | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Cytology images | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosisCite this page: Wu R. Solitary fibrous tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lungtumorsolitaryfibroustumor.html. Accessed May 11th, 2021.
Definition / general
- Similar to solitary fibrous tumors arising from pleura and other sites (bladder, CNS, colon, ear, eye, kidney, liver, mediastinum, nasal, prostate, soft tissue, thyroid) but arises as intrapulmonary mass
- May be difficult to diagnose with imaging and biopsy alone
Essential features
- Intrapulmonary solitary fibrous tumors are rare but appear to show similar characteristics to pleural based tumors
- Majority show NAB2-STAT6 gene fusion with nuclear STAT6 reactivity on immunohistochemistry
- Even bland tumors may have aggressive behavior, although most are indolent
Epidemiology
- Predominantly middle-aged to older adults (ages 40 to 80s), no sex predilection
Sites
- Arises most commonly from pleura, with uncommon inward growth into lung parenchyma
- Extremely rare to arise entirely within lung parenchyma
- Generally peripheral in location
Pathophysiology
- Growth in size over time may raise concern
- 10 - 15% behave in malignant fashion
Etiology
- Arise from fibroblastic elements of the submesothelial zone
- May develop from visceral pleura or interlobular septa but grow towards / into the lung parenchyma
Clinical features
- Often discovered incidentally on chest imaging but may show non-specific symptoms (cough, sputum, dyspnea, chest pain)
- Larger tumors (>7 cm) are associated with hypoglycemia, pleural effusion, pulmonary osteoarthropathy
Diagnosis
- Difficult to establish diagnosis based on imaging, bronchoscopic examination and limited biopsy specimens
- Immunohistochemistry is helpful to support diagnosis and rule out other entities
Radiology description
- Generally non-specific appearance
- Xray: abnormal shadow / nodule, discrete homogenously dense mass, lobulated
- CT: Well circumscribed nodule, enhances with IV contrast, may show necrotic foci
- PET: no / minimal uptake in most cases
- MRI: may show variable density and intralesional hemorrhage
Radiology images
Images hosted on other servers:
CT scan
Prognostic factors
- Tumors with overtly malignant histologic features are expected to behave as high grade sarcomas, but bland appearing tumors may also have an aggressive course (Am J Surg Pathol 2013;37:155)
- Clinical aggressiveness associated with atypical/malignant histology, primarily due to increased mitosis (Cancer Med 2015 Dec 21 [Epub ahead of print])
Case reports
- 7 year old boy with bronchial involvement (J Pediatr Surg 2010;45:249)
- 42 year old man who underwent FNA and core biopsy of lung mass (Diagn Cytopathol 2007;35:239)
- 71 year old woman with primary pulmonary solitary fibrous tumour with brain metastases (Eur J Cardiothorac Surg 2014;45:386)
- Intrapulmonary localized fibrous tumors (Ann Thorac Surg 2008;86:1360, Gen Thorac Cardiovasc Surg 2011;59:61)
Treatment
- Surgical resection based on size and location
Gross description
- Firm, rounded to ovoid, lobulated, well circumscribed, solid
- Tumor size variable, from 2 to 20+ cm
- Vaguely "whorled", gray-white cut surface
- Variable cysts, hemorrhage, necrosis
Gross images
Images hosted on other servers:
Excised tumor, pleura
Microscopic (histologic) description
- Markedly collagenous stroma ("ropey collagen") with irregularly distributed thick walled "staghorn" vessels and bland spindle cells
- Variable cellularity and histologic appearance, including "patternless pattern"
- Patterns: adenofibromatous (Int J Surg Pathol 2005;13:79), fibrosarcomatous, hemangiopericytic, neural-like plexiform
- Adenofibromatous appearance from entrapped normal airspaces at edge
- May have myxoid stroma
- Areas may resemble pleomorphic high grade sarcoma (pleomorphism, tumor giant cells, mitotic figures) intermixed with areas of conventional SFT
Microscopic (histologic) images
Images hosted on other servers:
CD34
Various stains, pleura
Cytology description
- Spindled to ovoid cells with "ropey" collagen in the background, cells with vesicular nuclei (Diagn Cytopathol 2007;35:239)
Cytology images
Images hosted on other servers:
Pleura
Positive stains
- Nuclear STAT6 (Cancer Med 2015 Dec 21 [Epub ahead of print])
- CD34, CD99, BCL2 in majority of cases (Am J Surg Pathol 2013;37:155)
- Vimentin, nuclear and cytoplasmic beta catenin (Arch Pathol Lab Med 2006;130:1503)
- p53 expression may be related to worse prognosis (Am J Surg Pathol 2008;32:1627)
Negative stains
Electron microscopy description
- Fibroblast-like with only basic intracellular organelles
Molecular / cytogenetics description
- NAB2-STAT6 gene fusion
- 90% of intrapulmonary SFTs demonstrate NAB2ex4-STAT6ex2/3 fusion variant (Cancer Med 2015 Dec 21 [Epub ahead of print])
Differential diagnosis
- Metastatic sarcoma
- Pulmonary hamartoma
- Sarcomatoid carcinoma
- Synovial sarcoma
