Fine needle aspiration cytology of follicular dendritic cell sarcoma of the stomach masquerading as gastrointestinal stromal tumor: A case report of a unique entity with emphasis on cytomorphology.

Follicular dendritic cell sarcoma (FDCS) is a rare malignant neoplasm, postulated to arise from follicular dendritic cells, with approximately 343 reported cases. Less than 100 cases of FDCS were in the gastrointestinal tract, with only four cases described in the stomach, none of them diagnosed on fine needle aspiration (FNA) cytology. We report here the first case of FDCS of the stomach diagnosed on FNA. Our patient is a 31-year-old male who presented with several years history of intermittent abdominal pain prompting occasional emergency-room visits. Imaging showed a 10.6 cm mass arising from the stomach, concerning for gastrointestinal stromal tumor. FNA cytology was performed using five passes with a 22-gauge needle. The smears were moderately cellular consisting of sheets and large, loosely cohesive clusters of ovoid to spindle cells with indistinct cytoplasmic borders and abundant cytoplasm, peppered with numerous small mature lymphocytes. The nuclei of the tumor cells were oval with finely granular chromatin with frequent nuclear grooves, pseudoinclusions, and easily recognizable mitotic figures. The tumor cells were positive for FDCS markers (CD21, CD23, and CD35).

A potential tradeoff between feeding rate and aversive learning determines intoxication in a Caenorhabditis elegans host-pathogen system.

Despite being the first line of defense against infection, little is known about how host-pathogen interactions determine avoidance. Caenorhabditis elegans can become infected by chemoattractant-producing bacteria through ingestion. The worms can learn to associate these chemoattractants with harm through aversive learning. As a result, the worms will avoid the pathogen. Evolutionary constraints have likely shaped the attraction, intoxication and learning dynamics between bacteria and C. elegans, but these have not been explored. Using bacteria engineered to express an acylhomoserine lactone chemoattractant and a nematicidal protein, we explored how manipulating the amount of attractant produced by the bacteria affects learning and intoxication in mixed stage populations of C. elegans. We found that increasing the production rate of the chemoattractant increased the feeding rate in C. elegans, but decreased the time required for C. elegans to learn to avoid the chemoattractant. Learning generally coincided with a decreased feeding rate. We also observed that the percentage of intoxicated worms was maximized at intermediate production rates of the attractant. We propose that interactions between attractant driven feeding rate and aversive learning are likely responsible for this trend. Our results increase our understanding of behavioral avoidance in C. elegans and have implications in understanding host-pathogen dynamics that shape avoidance.