Congratulation! Your Answer is Correct.

The correct answer is underlined below.

FNA Quiz 28 A 50 year-old man was admitted to hospital with a history of increasing shortness of breath and imaging studies revealed the presence of a 12.0 cm solid pleural-based mass in the upper lobe of the left lung. CT-guided fine needle aspiration and core needle biopsy of the mass was performed and representative images are illustrated below. Immunostains performed on the needle cores revealed that the tumor cells were diffusely positive for vimentin, focally positive for pan-cytokeratin, epithelial membrane antigen and bcl-2 protein, and negative for CD99, CD31, CD34, calretinin, desmin, smooth muscle actin, S-100 protein, and CD117. Fluorescence in situ hybridization (FISH) studies performed on one of the direct smears revealed the presence of a t(X;18) translocation in the tumor cells. Based on these findings, the BEST diagnosis is:

A.  Sarcomatoid carcinoma.

B.  Sarcomatoid mesothelioma.

C.  Extragastrointestinal stromal tumor.

D.  Pleuropulmonary synovial sarcoma.

E.  Solitary fibrous tumor/hemangiopericytoma.

Discussion: The direct aspirate smears (Panels A, B, C, and D) are hypercellular and show a uniform population of delicate spindle cells with scanty cytoplasm, fine nuclear chromatin, and small nucleoli consistent with a spindle cell neoplasm. Similar findings are present in the cell block section (Panel E) which shows a highly cellular neoplasm composed of interlacing fascicles of short spindle cells.  While the differential diagnosis would include all of the choices listed, the immunohistochemical findings effectively exclude extragastrointestinal stromal tumor (negative CD117 and CD34) and solitary fibrous tumor/hemangiopericytoma (negative CD34). Although the three remaining choices are not immediately distinguishable by the immunostain results given, the identification of a t(X;18) translocation by FISH is virtually diagnostic of synovial sarcoma. Synovial sarcomas are uncommon tumors, accounting for just 7 – 10% of all soft tissue sarcomas. Primary pulmonary sarcomas are also rare (0.1 – 0.5% of all primary lung malignancies) with the most frequently reported tumors being leiomyosarcoma, malignant fibrous histiocytoma, and fibrosarcoma. However, with the aid of ancillary techniques such as immunohistochemistry and cytogenetics, primary pleuropulmonary synovial sarcomas are being more frequently recognized.