malignant thymic neoplasms can be broadly divided into thymomas and thymic carcinomas , both of which exist almost exclusively in the anterior mediastinum .
thymomas have also been described in the neck , posterior mediastinum , lungs , base of the skull and pleural cavity [ 25 ] .
very few case reports have described thymomas occurring in the middle mediastinum [ 25 ] . unlike thymomas , thymic carcinomas
have only been observed in the anterior mediastinum . to our knowledge , this report will describe the first case of thymic carcinoma in the middle mediastinum .
a 55-year - old caucasian female presented with productive cough , dyspnea , chest pain and weight loss .
the patient 's medical history was significant for hypertension , hypercholesterolemia , dyslipidemia , chronic renal failure , gastroesophageal reflux disease and chronic anemia .
she was a 30 pack - year smoker and her mother was diagnosed with lung cancer .
an initial chest x - ray showed a large subcarinal mass . on computed tomography ( ct ) , a 6.2  5 cm tumor was detected in the subcarinal area ( figs  1 and 2 ) .
a bronchoscopy with transbronchial biopsy was performed , and the resulting pathological analysis was suspicious for malignant cells ; however , no specific tumor type was identified .
a positron emission tomography scan showed a large hypermetabolic subcarinal lesion with a standard uptake value of 14.3 , consistent with malignancy .
the differential diagnosis at the time included an infected bronchogenic cyst , esophageal duplication cyst or a malignant subcarinal lymph node .
thoracoscopic surgical resection was planned for diagnostic and therapeutic purposes . 
 figure  1:subcarinal tumor on preoperative ct of the chest , coronal cuts . 

prior to surgical resection , esophagoscopy and bronchoscopy documented the absence of any communication of this mass to the esophagus and airway .
one port was made at the mid - axillary line of the eighth intercostal space for the camera , in addition to two anterior and two posterior ports .
the dissection of the tumor began at the level of the inferior pulmonary ligament and posterior mediastinum , all the way to the azygous vein .
the esophagus was found completely adherent to the tumor , necessitating an esophageal myotomy for en bloc resection .
the anterior dissection proceeded at the level of the posterior atrial wall , the inferior and superior pulmonary veins , the main trunk of the pulmonary artery , and the membranous areas of the right and left main stem bronchi .
complete gross resection was observed at the conclusion of the operation . at the end of the procedure ,
air was insufflated into the esophagus to confirm the absence of any leaking from the mucosa .
the specimen consisted of an encapsulated red - brown tissue weighing 57 g , and measuring 5.5  4.5  5 cm .
some sheets of viable tumor cells were present , and these contained pleomorphic nuclei , vesicular chromatin , and prominent nucleoli .
the tumor cells were strongly positive for cam 5.2 , but negative for ck7 , ck5/6 , ck19 , calretinin , ttf1 , cea , afp , hcg , plap , cd5 and cd56 .
thus , thymic carcinoma was determined to be the most fitting diagnosis based on the morphology and staining .
the patient was referred for adjuvant radiation . at the most recent follow - up visit 9
months after surgery , the patient was well with no evidence of recurrence on ct scan .
all thymic carcinomas reported to date have been located in the anterior compartment of the mediastinum . to the best of our knowledge ,
this is the first case report of a thymic carcinoma occurring in the middle mediastinum .
the differential diagnosis of middle mediastinal tumors usually includes bronchogenic cysts , enterogenous cysts , neuroenteric cysts , pericardial cysts and lymphangiomas .
very selected cases of thymoma have been reported in the middle mediastinum [ 25 ] .
these are attributed to the presence of ectopic thymic tissue in the subcarinal area due to failure of the thymus to migrate into the anterosuperior mediastinum during embryological development [ 25 ] . by way of the same process
, it is therefore theoretically possible for these cells to undergo malignant degeneration into thymic carcinoma , although this has not been previously described .
when compared with thymomas , thymic carcinomas have considerably worse prognosis . when possible , complete surgical resection is the treatment of choice for thymic carcinomas [ 1 , 6 ] .
therefore , when planning surgical resection , it is important to consider malignant neoplasms as part of the differential diagnosis of middle mediastinal tumors .
although rare , thymic carcinomas and other malignant tumors of the middle mediastinum should be resected with negative margins , in order to decrease the risk of local recurrence and improve prognosis .
this is the first case report of a malignant thymic carcinoma occurring in the middle mediastinum at the subcarinal location .
this pathology , although rare , should be added to the differential diagnosis of middle mediastinal tumors . when planning surgical resection of such tumors , complete excision with negative margins should be attempted to minimize chances of local recurrence and improve prognosis .
 we report an extremely rare case of a thymic carcinoma occurring in the subcarinal location of the middle mediastinum , masquerading as subcarinal adenopathy . 
 a 6.2  5 cm mass was detected on computed tomography scan and found to be hypermetabolic on positron emission tomography scan . 
 transbronchial biopsy was performed and the mass was found to be suspicious for malignancy . 
 a thoracoscopic resection of the mass was performed and found to be thymic carcinoma . 
 the patient underwent a course of adjuvant radiation . to the best of our knowledge , 
 this is the first reported case of a thymic carcinoma resected from the middle mediastinum . 