Friday, October 24th, 2014

 

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Title:
Fine Needle Aspiration Biopsy of Intrabronchial Granular Cell Tumor
Authors:  P. Gˆran Elmberger, M.D., Ph.D., C. Magnus Skˆld, M.D., Ph.D., and Brian T. Collins, M.D.
  To the Editors: We encountered a case of intrabronchial granular cell tumor (GCT) presenting on fine needle aspiration cytology. A 59-year-old woman was referred to the Department of Respiratory Medicine due to suspected lung cancer and cerebral metastases. A computed tomogram (CT) of the brain showed 3 expansive processes with edema and were interpreted as consistent with multiple metastases. A chest radiograph revealed an infiltrate in the right lower lobe, and pulmonary CT confirmed expansion of the right intermediate and lower lobe bronchus, with peripheral infiltration and bronchiectasis (Figure 1). Bronchoscopy was performed. In the intermediate bronchus, a round, endobronchial tumor was seen. Transbronchial fine needle aspiration (FNA) biopsy and forceps biopsies were taken. Aspirate smears showed large, 3-dimensional, syncytial clusters as the predominant finding. These clusters were thick, and cellular elements could best be discerned at the borders of the large groups. The majority of cell groups were intermediate in size to large, with a high degree of cohesion. A few smaller, cohesive clusters were intermixed. On Giemsa staining these smaller clusters imparted an epithelioid, granulomatous appearance. Cytoplasm was abundant and relatively dense, with areas of fine granularity (Figure 2). At high power, Papanicolaou stain revealed small, monotonous, oval nuclei with fine chromatin and small, distinct nucleoli. The nuclear membranes were clearly demarcated, and the cytoplasm was granular (Figure 3). There was a profuse, inflammatory, granulocytic background in the aspirate smears. Bronchial biopsy verified a GCT. Pulmonary GCTs have been reported in the cytologic literature but were sampled primarily with bronchial brushings.1-3 Previous, detailed case reports on FNA have not appeared.4 In general, the cytology of pulmonary GCT corresponds to FNA findings in GCTs at other sites. The endobronchial location of this case is of interest, as are the cytomorphologic considerations it raises, based on the location as well as aspirate smear pattern. Based on the smear pattern, there are a variety of diagnostic considerations. For nonneoplastic conditions, granulomatous inflammation can have variably cohesive, epithelioid fragments with oval to spindled cells and abundant cytoplasm. Differentiating features include multinucleated giant cells, necrosis and lymphoid elements, typically lacking in GCT. A variety of specific primary pulmonary neoplasms should be considered. Acinic cell carcinoma can arise in the bronchus and present with obstruction. The morphologic smear pattern tends to have more single cells in the background, but stripped, naked nuclei can be present in either. Individual cells tend to have nuclei with darker chromatin and variably finely vacuolated cytoplasm. Application of S-100 immunocytochemistry can be required to make an accurate diagnosis. Recently, calretinin and alpha-inhibin have been reported as positive.5 Carcinoid tumor can be endobronchial in origin and can be a consideration when the sample is predominantly oncocytic, with abundant granular cytoplasm. Those tumors tend to be much less cohesive than GCT, with single cells and loose groups, and the nuclei present the main differentiating feature, with granular, "neuroendocrine" chromatin. As with any lung neoplasm, consideration should be given to a metastatic origin. Endobronchial metastases occur in 18-51% of autopsied patients with extrapulmonary malignant tumors, and the most common primary tumor sites are head and neck, breast, colon and kidney. Renal cell carcinoma is well known for first presenting in an extrarenal location; cells from an oncocytic carcinoma of renal origin are loosely cohesive in contrast to the overall high cohesion of GCT cells. The classic clear cell type has much more prominently vacuolated cytoplasm. Deavers described 20 cases of lung GCT, half of which presented with symptoms of bronchial obstruction.6 It is important to consider the differential diagnosis of GCT in FNA evaluation of endobronchial lesions. The application of strict morphologic criteria together with ancillary studies should permit an accurate classification.
Keywords:  granular cell tumor, aspiration biopsy, lung cancer, bronchial neoplasms
   
   
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