the multiple endocrine neoplasia type 1 syndrome ( men1 ) is a rare autosomal dominant hereditary cancer syndrome characterized by the development of endocrine tumors in different sites . the most frequent organs involved are the parathyroid glands , the endocrine pancreas and the anterior pituitary gland , sometimes associated with less frequent manifestations such as lipomas , carcinoid , adrenal tumors , skin angiofibromas and other types . lipomas originate from adipocytes with a prevalence rate of 2.1 per 1000 individuals and account for almost 80% of benign soft tissue tumors . these tumors develop , most likely , in subcutaneous tissue , but may occur in deeper sites making the diagnosis more difficult . they are generally well - capsulated , slow - growing and may appear single or in clusters . intrathoracic localizations are extremely rare and can occur at different sites such as in the bronchus , lung , diaphragm , mediastinum or thoracic wall . to our knowledge , this appears to be the first case reporting the massive intrathoracic lipoma in men1 . a 33-year - old female patient referred to our department with a diagnosis of primary hyperparathyroidism . her father had died at the age of 53 with a malignant non - functioning neuroendocrine pancreatic tumor . her sister had undergone total parathyroidectomy for primary hyperparathyroidism and genetic testing showed frameshift 908 gct in exon 5 of men1 gene . furthermore , she had breast cancer 1 ( brca-1 ) gene exon 11 mutation , inherited from her mother . the first surgery performed was a total parathyroidectomy with autotransplantation of a fragmented gland in a non - dominant forearm . after several months later the patient developed hypoglycaemic symptoms with a positive glucose fasting test and was diagnosed insulinoma . abdominal computed tomography ( ct ) showed three pancreatic nodules with a 1015  mm diameter , two of which were located in the pancreatic tail and another one in the head . endobronchial lesions were ruled out by bronchoscopy . due to a persistence hypoglycaemic crisis and no respiratory symptoms with normal arterial blood gas analysis , distal pancreatectomy was performed , extended to the pancreatic body with enucleation of a pancreatic head nodule . the post - operative course was complicated by intra - abdominal hemorrhage demanding surgical hemostasis . subsequently , the patient developed pancreatic a pseudo - cyst with an 8  cm diameter which was drained percutaneously . the patient was discharged on the 13th post - operative day and a control ct was scheduled to check out the thoracic findings described preoperatively . a massive lesion ( fig . thoracotomy at 6th left intercostal space was performed , accurately detaching the mass from the phrenic nerve and the left inferior lobe . the lesion originated from the inferior bronchus ; a complete excision was performed with the ligation of its vascular pedicle . the histopathological examination showed a 16  cm    12  cm    7  cm , 620-g , mature lipoma ( fig . the immunohistochemical examination was negative for the mouse double minute 2 ( mdm-2 ) protein . she is being accurately followed up and there is no evidence of signs of men-1 related manifestations . the men1 incidence is 1/30,000 individuals / year with a very high penetrance and equitable gender distribution . the familial form is characterized by a men1 case with one relative affected by one of the typical endocrine neoplasias . the typical tumors of such syndrome develop in different organs such as parathyroid glands , endocrine pancreas and the anterior pituitary gland . in association with these lesions , other endocrine and non - endocrine tumors , such as adrenal tumors , carcinoids , angiofibromas and lipomas have been reported . this may be helpful in the early diagnosis of men1 , before hormone - secreting tumors signs appear . the published incidence of lipomas in patients with men1 syndrome is wide ranging from 5% to 34% . the pathogenesis of the disease is based on the loss of heterozigosity ( loh ) of men1 gene , mapped on chromosome 11q13 , which encodes a 610 aminoacid nuclear protein . the mutation causes the inactivation of men1 tumorsuppressor gene , involved in the regulation of dna replication and repair . there is evidence in literature which proves which is the role of men1 gene in the pathogenesis of less specific men1 tumors , such as carcinoids and lipomas . more evidence showed that men1 mutation may be involved in the development of both men1-associated and sporadic lipomas and that 11q13 loh can vary in different tumors in the same patient . this suggests that the tumorigenesis is an independent somatic event involving the wild - type allele , which can occur in different tissues . studies conducted on sporadic lipomas show cytogenetic aberrations involving the 12q13q15 regions but it is argued whether all lipomas share one or more of the same breakpoint sites . it has been described that lipomas with breakpoints in 12q13 and 12q14 and those with normal karyotypes are clinically and histologically indistinguishable . lipomas are the most frequent benign soft tissue tumors and their incidence is not dependent on sex and age . the diagnosis is often incidental , following chest x - ray , as in our case ; the x - ray examination showed , a lipoma having a soft tissue density and occasionally a clear peripheral zone around the tumor . nevertheless further investigations such as ct or mri are needed to differentiate a lipoma from other lesions and to evaluate the relationship with the nearby structures . ct scan findings suggestive of lipoma are the presence of non - calcificating lesion with smooth rounded edges , originating from structures containing adipose tissue such as mediastinum , diaphragm , bronchus , lung or thoracic wall , with a density of 50 to 150  hu . although there are differences in radiological imaging between lipoma and liposarcoma , the definitive diagnosis is achieved only by means of a histopathological examination . lipomas are composed by sheets of mature adipocytes without any mitotic activity and are separated by incomplete fibrous septa . liposarcomas have five histological subtypes among which there is the well - differentiated and dedifferentiated form . the former is characterized by the presence of lipoblasts and atypical stromal cells with several mitoses and hypercromatic nuclei inside a mature fat tissue . the latter , instead , has a morphology which is very similar to a fibrosarcoma or a histiocitoma and it is generally close to well - differentiated elements . the immunohistochemical stain showing the mdm-2 and cyclin - dependent kinase 4 ( cdk-4 ) hyperexpression enables a certain diagnosis of dedifferentiated liposarcoma . , therefore , be radical although some reports show that the mass growth may be halted even after incomplete removal . hence , for it is fundamental to follow up these patients very accurately , by means of physical examination and radiological imaging focusing on initial signs and symptoms that might appear . all authors contributed to this work : alessandro sturiale , tiziana cavalli and carmine santomaggio collected the data , francesco giudici , alessandro sturiale and giovanni alemanno analyzed data , alessandro sturiale , giovanni alemanno , francesco giudici , rami addasi and giulia meoni wrote the manuscript and francesco tonelli and maria luisa brandi supervised all the manuscript.key learning pointshow to treat a rare case of intrathoracic lipoma in men1 syndrome.the importance to follow - up these patients . how to treat a rare case of intrathoracic lipoma in men1 syndrome.the importance to follow - up these patients . how to treat a rare case of intrathoracic lipoma in men1 syndrome .
introductionthe multiple endocrine neoplasia type 1 ( men1 ) is a rare autosomal dominant syndrome characterized by the onset of hyperparathyroidism , gastroenteropancreatic neuroendocrine tumors and pituitary lesions.presentation of casethis appears to be the first described case of a massive intrathoracic lipoma in men1 . 
 the patient was affected with primary hyperparathyroidism treated with a total parathyroidectomy followed by a distal pancreatectomy for insulinoma . at follow - up , the computed tomography showed a massive lesion on the left emithorax suggestive of a lipoma . at the onset of a mild dyspnea we decided to perform 
 the surgical excision of the mass obtaining a complete relief of the symptoms.discussionthis case is evidence of the importance of a strict follow - up of such patients.conclusionlipomas are the most frequent benign soft tissue tumors . 
 they are usually sporadic but are sometimes related to hereditary syndromes . 
 intrathoracic localizations are rare and can arise mainly in the mediastinum , bronchus or lung . 
 the diagnosis is often incidental ; despite preoperative imaging will accurately show the features of the lesions , it is impossible obtain an accurate diagnosis - hence , the treatment of choice remains the surgical excision .