Macroscopy: Sectioning shows homogenous firm grey tissue attached to a thin strip of the lung parenchyma, 1 mm in thickness. The stapled resection margin is inked black, with the remainder inked blue. "Right chest wall mass". An excision of lobulated cream-coloured/pink tissue. No normal lung tissue is identified, nor is any obvious resection margin. Scant adipose tissue with attached. Sectioning shows lobulated whorled cream-coloured lesional tissue with prominent fibrosis. No necrosis, haemorrhage or calcification is present. The external surface is inked blue.
Microscopy: The sections show a nodular lesion arising at the visceral pleural surface, comprised of haphazard arrays of spindled cells with intervening thick ropey collagen, and scattered ectatic, irregularly branched and thin-walled vessels. The spindled cells have tapered nuclei, evenly distributed nuclear chromatin and occasional small nucleoli, and show only minimal variation in size and shape. Scattered chronic inflammatory cells are seen. Mitotic figures are rare. The lesion is present at the pleural surface and focally abuts the stapled resection margin. A small amount of uninvolved perilesional lung parenchyma present near the stapled resection margin shows type 2 pneumocyte hyperplasia.
The sections show a tumour with a multinodular architecture, traversed by fibrous connective tissue bands of variable width. The tumour is comprised of haphazard arrays of spindled cells with intervening thick ropey collagen, with scattered ectatic and irregularly branched, thin-walled vessels throughout. The spindled cells are plump, blunt-ended, closely packed and exhibit moderate variation in nuclear size. Chromatin is fine and evenly distributed and cytoplasm small to moderate in amount and showing variable eosinophilia. Whilst the bulk of the tumour is highly cellular, areas of hypocellularity associated with myxoid stromal change are present. Focal necrosis is identified. Mitoses are numerous, numbering up to 8 within 2 square millimetres). Evidence of dedifferentiation is not observed. Angiolymphatic invasion is not identified. Tumour extends to the resection margins of the specimen. A small amount of alveolates lung parenchyma is noted and, in this section, the appears to arise at the visceral pleural surface. A small amount of uninvolved mature adipose tissue is noted.
Tumour cells show nuclear immunoreactivity with antibodies against STAT6, cytoplasmic immunoreactivity with antibodies against Bcl-2, CD99 and beta-catenin, and patchy cytoplasmic immunoreactivity with antibodies against CD34.
Immunohistochemistry with antibodies against pan-cytokeratins, ALK1, CK5/6, desmin, SMA, caldesmon, podoplanin, S100, calretinin, WT1, EMA and p53 is negative.
Conclusion: Solitary fibrous tumour.