Pulmonary synovial sarcoma

Case contributed by Frank Gaillard
Diagnosis certain



Patient Data

Age: 20 years
Gender: Female

CXR demonstrates a very well circumscribed mass in the left upper zone. The differential is that of a solitary pulmonary mass. 

Case Discussion

The patient went on to have a lobectomy. 


Macroscopic description

A lobectomy specimen, consistent with left upper lobe, 140 x 130 x 30 mm, with attached bronchial remnant, 15 mm in diameter and 6 mm long. In the middle of the left upper lobe towards to the anterior surface, is a relatively well circumscribed, irregular, soft shiny and tan tumor, 60 x 35 x 45 mm. It is 4 mm from the pleural  surface. The overlying pleura is smooth and glistening. The tumors appears to  be within 1 mm of  the bronchus, but does not appear to invade through it. It is approximately 5 mm from the bronchial resection margin. Elsewhere, the lung parenchyma is variegated brown tan, with patchy, pale regions, more  prominent towards the superior aspect and anterior inferior aspect.

Microscopic description

Sections from the macroscopically described lesion show a well circumscribed, highly cellular neoplasm composed of interlacing fascicles of plump spindled cells separated by small or ectatic thin-walled blood vessels. The tumor cells possess overlapping, large, elongate ovoid nuclei with multiple small nucleoli, and frequent mitotic figures are noted  (21/10hpf).   There  are large  areas  of  necrosis. There are also less cellular, edematous foci scattered throughout. In areas, tumor bulges into an bronchioles, undermining epithelium, but there is no cystic component. No lymphovascular space invasion is seen, and the lesion is clear of the pleural surface. No rhabdomyosarcomatous or chondroid differentiation is seen. Immunohistochemical  stains have been performed, and the tumor cells show diffuse immunoreactivity for vimentin, CD99, bcl-2 and CD56. There is focal immunoreactivity for calretinin and weak and patchy immunoreactivity for epithelial membrane antigen. The tumor cells are negative for cytokeratins (AE1/AE3, cytokeratin 7, cytokeratin 5/6), S100 protein, gp-100, desmin, smooth muscle actin, CD34, synaptophysin and TTF-1. Overall, the features are most in keeping with a monophasic pulmonary synovial sarcoma.   

FISH studies were POSITIVE  for SYT (18q11.2) breakapart rearrangement in >50% of cells examined which is consistent  with a diagnosis of synovial sarcoma. The accuracy of these results is dependent on the correct identification of tumor on the sections  provided, and the assumption that positive results will be identified by a large proportion of cells within the tumor having a rearrangement.

Final diagnosis

Malignant spindle cell tumor with features favoring monophasic pulmonary synovial sarcoma.

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