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palatal sialolipomas are rare and were identified as a definite entity in 2001 . to our knowledge , less than 10 cases from the hard palate are reported . here
, we report a case of hard palate sialolipoma , peculiar by the intratumor malformation - type vascular patterns .
a 67-year - old man presented with a median mass of the oral hard palate , noticed since several years .
focally , the lesion was surrounded by a fibrous tissue rim mainly at the interface with the oral mucosa ( which was not ulcerated ) .
deeply , there were minor salivary gland lobules , interspersed completely or in part by adipocytes .
the salivary gland showed focal lymphocytic infiltrate , a focus of fibrous regression with ductal atrophy as well as zones of ductal basal cell hyperplasia and/or large duct dilatation .
however , numerous hemorrhagic areas were seen in marginal zones , probably in relationship with intraoperative vascular section / rupture .
rare nerves were seen in close association with adipocyte , glandular lobules and large vessels at the periphery of the specimen .
smooth muscle actin was expressed in the vessel wall and consisted of a rim of positive cells of varied thickness .
endothelial cells were positive for cd31 and negative for d2.40 ( expressed in superficial , pericapsular lymphatics ) .
photomicrograph showing lesional tissue consisting mainly of adipose tissue ( asterisk ) covered by an intact epithelium with a fibrous band below the epithelium ( black arrows : vessel walls ) ( h&e stain , x25 ) , ( b ) lesional tissue showing large , ramified vessels with irregularly thickened wall ( black arrows ) and salivary gland lobules ( arrow head ) ( h&e stain , x50 ) , ( c ) areas showing salivary gland lobules ( arrow head ) and adipose tissue ( asterisk ) ( h&e stain , x25 ) , ( d ) high power view showing the salivary gland lobules ( arrow head ) ( h&e stain , x200 ) ( asterisk : adipose tissue ) ( inset : photomicrograph showing adipose tissue and nerves / arrows , h&e stain , x100 ) , ( e ) vessel walls showing papillary projections ( white arrows ) ( h&e stain , x200 ) ( inset : low power view of the vessel 's wall ( h&e stain , x25 ) , ( f ) vessel wall showing positivity for smooth muscle actin ( black arrows ) ( ihc stain , x50 ) .
here , we report a case of sialolipoma of the hard palate peculiar by the presence of intratumoral malformation - type vascular patterns . several blood vessels were large , with thickened wall and rare papillary projections or tufts .
this latter morphological feature , more frequently reported in vascular malformations than in angiomas when considering the gastrointestinal location , rather suggested a vascular lesion of malformation - type than an associated angioma or an angiolipoma - type lesion . moreover
, the presence of nerves favored the hypothesis of vascular malformation type lesions . with regard to hard palate
angiolipomas , defined as lipomas with a prominent capillary network , these tumors are rare to our knowledge , reported in two cases : one in a young adult man and one in a girl .
they are located laterally on the right or left side , age predilection is mainly between 60 - 70 years ( although a symptom duration of 15 days to 10 years ) and measure more than 4-cm in size . the size of hard palate sialolipomas ( 11.8 cm ) and their age distribution reported in the literature
several other adipocyte - abundant lesions are also to be ruled out . a traumatic pseudolipoma was not considered since the evolution was long and reparative signs such as fibrosis and inflammation were limited .
the diagnosis of lipomatosis was also not considered due to the presence of capsular tissue neither was an infiltrating lipoma considered , although this lipoma - type can contain large vessels .
another hypothesis is that of entrapped vessels in adipose tissue , difficult to sustain for a low - fat location such as the hard palate .
the origin of lipomatous lesions of the hard palate , is similar to that of oral lesions and remains incompletely elucidated .
lipoblastic embryonic cell nests , metaplasia of muscle cells and fatty degeneration can be incriminated as originary events while trauma ( with or without soft palate tissues dislocation ) , infection , chronic irritation or hormone imbalance can be considered as favoring factors .
whether an altered oxygenation as a result of intra - tumor malformative vessel network may have an impact on a limited growth although there was a long evolution period remains to be further elucidated .
it should also be taken into consideration that losartan - treated patients show a higher body mass index as compared to placebo - treated patients ( despite randomization ) , although losartan does not affect this index .
however , adipose hyperplasia or submucosal adipose involution in the context of overweight / obesity may be considered among the hypotheses for histogenesis of fat lesions of the hard palate .
interestingly , a hard palate lipomatous lesion of osteolipoma type is reported to be associated with cleft palate in a 6-year - old boy .
cleft palate patients are also reported to rarely show vascular malformations either de novo , reported in pediatric cases or as a manifestation after post surgical treatment , reported in a 25-year - old woman .
whether in the present case a subclinical osseous malformation was present remains difficult to be determined due to the lack of computed tomography scan .
the microscopic features of the tumor in the present case suggest that malformation - type vascular patterns may occur in sialolipomas of the hard palate .
this morphological vascular peculiarity should be acknowledged since it can be a possible source of hemorrhage .
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the patients understand that their names and initials will not be published and due efforts will be made to conceal their identity , but anonymity can not be guaranteed there are no conflicts of interest .
the authors certify that they have obtained all appropriate patient consent forms . in the form the patient(s )
has / have given his / her / their consent for his / her / their images and other clinical information to be reported in the journal .
the patients understand that their names and initials will not be published and due efforts will be made to conceal their identity , but anonymity can not be guaranteed
palate sialolipomas are rare . 
 less than 10 cases located in the hard palate are reported to our knowledge . 
 we report a case of hard palate sialolipoma , peculiar by the intratumor vascular patterns . a 67-year - old man presented with a 1.5 cm lesion of the oral hard palate . 
 the lesion was surgically resected . 
 on microscopy , the lesion , partly encapsulated , consisted of a proliferation of mature adipocytes containing normal minor salivary gland tissue and branching intratumoral vessels of varied size with irregularly thickened wall and papillary projections or tufts . 
 the microscopic features of the tumor we report suggest that vascular malformation - like patterns may occur in sialolipomas of the hard palate . 
 this morphological vascular peculiarity should be acknowledged since it may represent source of hemorrhage .