benign deep thoracic wall cyst is uncommon ; however , operative management using an endoscopic approach should be reserved primarily for symptomatic cases with multiple comorbidities , where multiple attempts at aspiration have failed because it is associated with less postoperative pain , lower morbidity and faster recovery [ 14 ] .
a 62-year - old caucasian male presented with swelling and fullness in the left posterior chest
. physical examination revealed a morbidly obese white male with a non - tender fluctuant mass on the left side of the upper back .
the patient had two motor vehicle accidents that caused a lower right - sided lumbar injury .
his past medical history was significant for hypertension , hyperlipidemia , sleep apnea , osteoarthritis , gastroesophageal reflux disease and chronic mild asthma .
computed tomography ( ct ) scan of the chest demonstrated a large cystic mass between the posterior aspect of the thoracic ribs and deep to the muscles of the left back and scapula .
chest magnetic resonance imaging delineated a large cystic mass extending from the level of the lower neck to just above the level of the diaphragm measuring 11 cm transversely , 4.5 cm anteroposteriorly and 23 cm craniocaudally ( fig .  1 ) . 

figure  1:(left ) chest ct scan shows the large cystic mass ( arrow ) between the left posterior ribs and muscles of the left back and scapula .
( right ) chest mri shows the large cystic mass extending from the level of the lower neck to just above the level of the diaphragm .
( left ) chest ct scan shows the large cystic mass ( arrow ) between the left posterior ribs and muscles of the left back and scapula .
( right ) chest mri shows the large cystic mass extending from the level of the lower neck to just above the level of the diaphragm .
when the mass returned 2 weeks later , he was referred to our institution for further treatment . due to symptoms referred to the cyst and the lack of response to aspiration
the patient underwent general endotracheal anesthesia and was placed in the right lateral decubitus position .
a 2.5-cm longitudinal incision was made at a paramedian position on the left mid - back and it was carried through the level of the fascia by cautery .
the paraspinous muscle fibers were separated and the bottom of the cyst was bluntly dissected free and the cyst was aspirated of its serous contents .
the balloon was inflated to grapefruit size and left inflated for 2 min for hemostasis .
the balloon dissector created a larger space beneath the cyst and along its lateral margins .
the balloon was then replaced with a hasson trocar , and two additional 5-mm trocars were placed under direct vision to allow access to the co2-filled cavity ( fig .  2 ) .
using a combination of blunt and electrocautery dissection , the cystic lesion was circumferentially freed from the trapezius muscle and cervical structures .
once freed , the cystic mass was removed in its entirety through the hasson trocar site .
two 15-french round jp drains were inserted through the 5-mm trocar sites and placed to grenade suction . 

histologic analysis of the unilocular cyst revealed a primarily fibrous wall with some adipose tissue and associated vasculature .
the cyst lacked a true epithelial lining and any malignant features such as hypercellularity , hyperchromasia , cellular pleomorphism or increased mitoses ( fig . 
the final pathologic diagnosis was that of a benign , fibrous - walled cyst . 

while benign cysts are common within the skin and subcutaneous tissues of the posterior thorax , lesions deep to the muscles are rare . with aspiration of clear fluid devoid of malignant features ,
cysts such as these should undergo aspiration and , if reaccumulation occurs , repeat aspirations with injection of a sclerosing agent or surgical management are reasonable . with the potential need for repeated aspirations and sclerotherapy , our patient opted for cyst removal .
while novel approaches are reported in abdominal wall surgery [ 1 , 3 ] , no reports document this technique for deep chest wall surgery .
the balloon dissector and endoscopic resection facilitated free dissection of this large chest wall cyst .
we have found no published reports of a deep thoracic cyst resembling our patient 's cyst in terms of histology or location .
the differential diagnosis is not long , consisting primarily of seroma and secondarily of a synovial or ganglion cyst .
these entities do not usually have a true epithelial lining , and they tend to occur in areas of previous trauma or surgery . our patient had undergone previous cervical spine surgery , which conceivably could be the cause of this cystic lesion .
however , given its location off the midline , deep - seated nature against the rib cage , and virtually no scarring of the neck near the cyst , we believe that this cyst was unlikely related to the previous operation .
other diagnoses to consider include sarcoma ( which can be ruled out by absence of malignant features on pathology ) , epidermal inclusion cyst ( unlikely given the large size , location deep to the dermal and subcutaneous region , and lack of squamous epithelial lining with keratinization ) and abscess ( unlikely given absence of inflammatory cells ) . given this patient 's cyst , it did not fit well into any of the above categories , our pathologists suggest that it is a benign and fibrous - walled cyst .
 we present a 62-year - old male with a recurrent cyst in the left posterior chest . 
 mri demonstrated a fluid - filled cavity measuring 23 cm in length and 11 cm in width . 
 the cyst was aspirated demonstrating clear serous fluid . however , the cyst returned and he was referred to us for further treatment . 
 the cyst was excised through a minimally invasive approach using a combination of blunt and electrocautery dissection . 
 the cystic lesion was circumferentially freed from the trapezius muscle and cervical structures . 
 pathologic examination revealed a benign , fibrous - walled cyst without a true epithelial lining . 
 there are no published reports of a deep thoracic wall cyst resembling this case in terms of histology or location . 
 this patient is free of recurrence 1 year later . 
INTRODUCTION
CASE REPORT
DISCUSSION