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- diagnostic techniques and procedures
- lung neoplasms
- morphological and microscopic findings
A 68-year-old man presented with a well-delimited tumour measuring 31×28 mm in the right upper lobe of the lung (figure 1A) that had been detected by chest CT 5 years earlier. A recent CT scan showed that the tumour had grown to 42×36 mm (figure 1B). A core biopsy was performed followed by tumour excision with an atypical wedge resection segmentectomy and intraoperative cytology touch imprint examination.
What is your diagnosis?
Biphasic synovial sarcoma.
Biphasic malignant mesothelioma.
Metastatic CD34+ spindle cell tumour (GIST, Kaposi sarcoma, mammary-type myofibroblastoma).
Atypical solitary fibrous tumour.
Solitary fibrous tumours (SFTs) were originally described in the pleura, but they have since been reported at virtually all anatomic sites. The vast majority of SFTs are clinically and morphologically benign, but around 5% show malignant behaviour, including metastasis. An even smaller proportion have morphological features associated with aggressive behaviour, namely, increased mitotic activity (>4 mitoses/10 high-power fields (HPFs)), nuclear atypia, hypercellularity and necrosis.1 2 This more aggressive variant, known as atypical SFT, resembles conventional SFT, but it has atypical histological features that are each suggestive of malignancy (box 1). Its immunohistochemical characteristics are also analogous to those of conventional SFTs (CD34 and STAT6 positivity). As prognosis is unpredictable, long-term follow-up is recommended. Nuclear expression of STAT6 is a surrogate marker for the NAB2–STAT6 fusion gene, located in region 12q 13. …
Handling editor Iskander Chaudhry.
Contributors JL made the diagnosis, prepared the manuscript, recorded clinical information and provided the figures. LA diagnosed and provided CT scans.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.