paraneoplastic pemphigus ( pnp ) is an extremely severe autoimmune blistering disease associated with neoplasms ; the disease is most commonly of lymphoproliferative origin and presents a high mortality 1 . follicular dendritic cell ( fdc ) sarcoma is rare and classified either as a conventionaltype or as an inflammatory pseudotumor ( ipt)like variant . iptlike fdc sarcoma is a rare neoplasm with different histologic appearance and behavior from those of the classical fdc sarcoma 2 . a review of 38 cases of iptlike fdc sarcoma reveals that this tumor occurs predominantly in females with a predilection for liver and spleen , with a strong association with epstein less than 30 cases of fdc sarcoma have been reported , in which the patients were diagnosed with myasthenia gravis ( mg ) or pnp 3 , 4 . moreover , two cases of castleman 's disease were associated with mg and pnp , suggesting a putative alternative linkage of pnp , mg , and the associated neoplasms 6 , 7 . to date , we have not found any reports on iptlike fdc sarcoma associated with mg or pnp . a 60yearold chinese woman presented a 6month history of recurrent weakness and increasing upper extremity fatigue , fluctuating diplopia , and ptosis of both eyes , finally showing dysarthria and dysphagia . during 6 months several masses had been found in her left axillary region and neck for 15 years , and the masses were resected every 4 years without radiotherapy or chemotherapy . the last surgery was 2 years prior to the study . after admission , thoracic computed tomography ( ct ) showed several masses in the left axillary and neck , and the diameter of the maximal tumor was 6.4 cm . core needle biopsy revealed spindle tumor cells arranged in a storiform pattern with scattered lymphocytes ( fig . spindle tumor cells contained vesicular chromatin , small nucleoli , and thin smooth nuclear membranes ( fig . immunohistochemical studies revealed that the tumor cells were positive for ki67 ( + 20% ) ( fig . 2a ) , vimentin , cd21 , cd35 , cd20 , egfr , cd68 , s100 ( fig . 2b ) , cd1a , cd3 , and cd79a and negative for ema , ck , cd23 , cd34 , hmb45 , cd30 , mpo , and lysozyme . however , ebvencoded rna was detected by in situ hybridization and was negative . ( a ) microphotograph showing spindle tumor cells arranged in a storiform pattern with scattered lymphocytes ( 10 ) . ( b ) spindle tumor cells contained vesicular chromatin , small nucleoli , and thin smooth nuclear membranes ( 20 ) . ( b ) some of the spindle cells are positive for s100 ( 10 ) . after admission , treatment was immediately started with pyridostigmine at a dose of 60 mg three times per day following a subtle improvement of muscle weakness . five days later , the patient developed severe dyspnea , and then , an emergency intubation and mechanical ventilation were administered . immunoglobulin ( 0.4 g / kg / day 5 days ) and steroid pulse therapy ( methylprednisolone sodium succinate , 1000 mg daily  3 days , gradually tapered off ) were given . sixteen days after treatment with immunoglobulin and steroids , the patient was successfully detached from the respirator . mechanical ventilation was again administered . after steroid and immunoglobulin treatment failure , rituximab at a dose of 500 mg ( 330 mg / m/week ) after four courses of rituximab treatment , the skin lesions and muscle weakness were almost recovered , and ventilator weaning was successful . three weeks after discharge , she was hospitalized with severe generalized blistering skin eruptions and polymorphic erythemas and mucosal ulcerations ( fig . 3 ) , which were considerably worse than those in the previous occasion but without myasthenia symptoms . then , she was treated with immunoglobulin ( 1 mg / kg per day ) without improvement of mucocutaneous lesions . we describe the extremely unusual association of an iptlike fdc sarcoma with pnp and mg . the pathogenesis is thought to be due to the production of antibodies against tumorderived antigens ; the antibodies may attack components sharing the same or a similar epitope 8 . 10 reported a case in which pnp associated with fdcs showed a good response to a treatment plan that included dexamethasone , surgery , and chemotherapy . our observations on this case indicate that rituximab could be an effective alternative therapy in the treatment of pnp and mg . however , pnp recurred catastrophically , perhaps because the standard treatment dose was not achieved and surgical resection of tumors was not performed . the patient presented multiple local recurrences without systemic dissemination for a long period , suggesting an indolent clinical course . considering the high mortality of pnp , we should pay more attention on the diagnosis and treatment of iptlike fdc sarcoma .