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nonneoplastic hemorrhagic lesions causing mucosal swelling and bone destruction can develop in the maxillary sinus .
this type of lesion was reported in the japanese literature in 1917 as a  blood boil of the maxillary sinus  by tadokoro and is comparatively well known in japan as one of the differential diagnoses of maxillary carcinoma . however , in the english literature , this type of lesion tends to be referred to as hemangioma of the maxillary sinus , organized hematoma of the maxillary sinus , or organized hematoma of the maxillary sinus mimicking tumor [ 18 ] .
although their clinical manifestations are very similar , the relationships between these entities have not been described .
histologically , a combination of dilated vessels , hemorrhage , fibrin exudation , fibrosis , hyalinization , and neovascularization was characteristic .
therefore , either of the terms hemangioma or hematoma reflects the complete histological picture . in this paper , we report the clinicopathological characteristics of this entity and the relationship between the imaging and histopathological findings .
to evaluate the clinicopathological entity of the organized hematoma , we recruited subjects with lesions that met the following criteria .
( 1 ) ct demonstrated an expanding unilateral maxillary lesion , with thinning or destruction of the surrounding bony tissue ; ( 2 ) mri demonstrated a heterogeneous mass ; ( 3 ) macroscopically , a mass with a hemorrhagic and heterogeneous appearance was observed ; ( 4 ) histologically , nonneoplastic tissue with mucosal hemorrhage was observed .
of all the patients referred to our department between 1996 and 2010 with suspected maxillary tumor , five met these criteria .
these patients underwent clinical evaluation , followed by either transmaxillary or endonasal endoscopic sinus surgery and histopathological examination of the resected tissue . for immunohistochemical detection of cd31 , cd34 , and periostin , we used the labeled streptavidin - biotin - complex ( sabc ) method .
the sections were autoclaved for 10  min at 120c in citrate phosphate buffer ( ph 6.0 ) for antigen retrieval .
the sections were then incubated with skim milk normal in phosphate - buffered saline ( pbs ) for 10  min to block nonspecific background staining .
monoclonal anti - cd31 and cd34 antibodies were purchased from dako japan ( tokyo , japan ) .
a polyclonal anti - pendrin or anti - periostin antibody was generated by immunising the rabbits with specific peptides .
polyclonal antibody against pendrin was applied as a primary antibody at a dilution of 1  :  100 and incubated at 4c overnight .
polyclonal antibody against periostin was applied as a primary antibody at a dilution of 1  :  500 and incubated at 4c overnight .
after the sections had been washed with pbs , biotinylated goat anti - rabbit igg was applied , and they
immunostained sections were assessed at 200x  magnification under an olympus microscope with an eyepiece reticle .
cell counts are expressed as means per high - power field ( 0.202  mm ) .
at least two sections were immunostained , and more than five areas were evaluated via the reticle .
results are expressed as number of positive cells per field , as follows : (  ) : negative ; ( + ) : fewer than 10 cells in each high - power field ( 400 ) ; ( + + ) : 10 to 20 cells ; ( + + + ) : more than 20 cells .
patient characteristics and the clinical features of the five cases are summarized in table 1 .
the clinical features resembled those of maxillary carcinoma . the most frequently observed primary sign was recurrent epistaxis , although a wide variety of clinical features were observed , including nasal obstruction , cheek pain , and nasal pain . in most cases ,
the clinical course before diagnosis had been a for few months ; however , one patient visited an ent clinic because of hemorrhage from right nasal cavity mass and right nasal obstruction that had gradually enlarged over the course of 11 months .
ct showed unilateral maxillary masses with thinning or destruction of the surrounding bony structures ( figure 1 ) .
the masses were well demarcated from the surrounding structures and heterogeneous in signal density on both t1-weighted , t2-weighted , and gd - dtpa - enhanced images ( figure 2 ) .
ct and mri provided sufficient information to differentiate these lesions from malignancy ( table 2 ) .
a transmaxillary surgical approach was used in two patients and endonasal endoscopic sinus surgery in three patients .
the masses had firm capsules and were therefore removed easily , even in all cases in which the lesion extended from the maxillary sinus . before the surgery , three patients underwent angiography , which revealed that the maxillary artery was the feeder artery .
two of the patients had strongly enhanced lesions , which were embolized with gelform ( table 3 ) .
histologically , the specimens consisted of dilated vessels , hemorrhage , fibrin exudation , fibrosis , hyalinization , and neovascularization , without tumor cells ( figure 3 ) .
cd34-positive cells ( progenitors of endothelial cells ) were also observed in the specimens ( figure 4 ) .
these characteristic findings were generally seen in separate sections from each mass ; the pattern of the mixture of findings differed among parts of the same mass , masses from the same patient , and patients .
the appearance of the findings also varied among different parts of the masses and among patients . to obtain all of these findings , we needed to examine several sections from different parts of each mass ( table 4 ) .
these characteristic findings were all subepithelial , and the lining of the epithelium was intact .
followup to date ( range from 6 to 108 months ) has demonstrated all patients to be free of recurrence .
preoperative ct showed a heterogeneously enhanced mass expanding out of the maxillary sinus , with thinning or destruction of the adjacent bone .
this expansion did not exhibit an invasive pattern but is commonly seen in malignancy , so the ct findings were not specific to this disease .
mri was able to demonstrate the apparent morphological heterogeneity of this disease and thus clearly differentiated it from neoplasms and mucoceles . a heterogeneous signal intensity on mri was commonly observed .
the mucosa was well enhanced on t1-weighted images with contrast and had high signal intensity on t2-weighted images .
in addition , the central part of the lesion had low signal intensity on t1-weighted imaging and high signal intensity on t2-weighted imaging and was well enhanced .
these findings suggested that this central region contained blood with a low flow speed , thus matching the pathological finding of hematoma .
this biphasic appearance is an important imaging aspect of this lesion and needs to be considered in the differential diagnosis before a decision is made on a treatment strategy .
recognizing the location of the hematoma preoperatively could be useful for avoiding intraoperative bleeding from the mass .
microscopic examination revealed dilated vessels , hemorrhage , fibrin exudation , fibrosis , hyalinization , and neovascularization in the subepithelium .
the appearance of these findings varied among different parts of the masses , and as for the disease etiology , omura et al .
first , a blood clot accumulates in the closed space owing to bleeding of various causes , including hemangioma formation , facial injury , or inflammation .
next , necrosis , fibrosis , and hyalinization occur in turn , and neovascularization develops as part of the biological healing processes . as a result , the new vessels become weak , and rebleeding might easily occur . to examine this negative spiral theory immunohistopathologically , cd31 , cd34 , and periostin were used for immunostaining .
these results showed that the endothelial cells kept their structural integrity and dilated pattern in limited areas .
cd 34 is expressed on the progenitors of endothelial cells and might play an important role in neovascularization and wound healing [ 911 ] .
periostin is a regulator of fibrosis and collagen deposits , and although it has been recognized for the important role it plays in myocardial repair / remodeling following myocardial infarction , there are indicators that its overexpression in the nasal mucosa contributes to tissue repair and fibrosis .
surgery is mandatory to remove the organized hematoma as first - line treatment . to differentiate the organized hematoma from a malignant tumor , the complete absence of neoplastic cells in the totally removed specimen
thus , total removal under general anesthesia is usually performed , and the surgical procedure should be chosen depending on the size of the lesion .
ess should be considered as the first line in limited lesion with adequate working space for the endoscopic operative field . in case of large lesion with thinning the bone structure of the paranasal sinuses
there was little difference in the intraoperative bleeding volume between patients who received endoscopic sinus surgery ( ess ) and those who underwent the transmaxillary approach . to decrease
the intraoperative bleeding volume , embolization of the feeder artery is necessary if the feeder artery is identified by angiography . in our series
, angiography was performed in only three patients and embolization in two . in the two patients that received embolization ,
the volume of intraoperative bleeding was less than that in the patients who did not receive embolization . in summary
organized hematoma of the maxillary sinus was characterized pathologically by a mixture of bleeding , dilated vessels , hemorrhage , fibrin exudation , fibrosis , hyalinization , and neovascularization .
objective . to study the clinical and pathological characteristics of patients with organized hematoma with malignant features in maxillary sinuses . 
 subjects and methods . 
 this was a retrospective study of five patients who were treated surgically for organized hematoma . 
 the preoperative ct and mri findings were studied clinically . 
 the expressions of cd31 , cd34 , and periostin in surgical samples were investigated by immunohistochemistry . 
 results . 
 the clinical features of organized hematoma , such as a mass expanding from the maxillary sinus with bone destruction , resembled those of maxillary carcinoma . 
 however , ct and mri provided sufficient and useful information to differentiate this condition from malignancy . 
 surgical resection was the first - line treatment because of the presence of a firm capsule . 
 characteristic histopathological findings were a mixture of dilated vessels , hemorrhage , fibrin exudation , fibrosis , hyalinization , and neovascularization . the expressions of periostin , cd31 , and cd34 were observed in organized hematoma of the maxillary sinus . 
 conclusion . 
 the expressions of periostin , cd31 , and cd34 were observed in organized hematoma of the maxillary sinus . 
 organized hematoma is characterized pathologically by a mixture of bleeding , dilated vessels , hemorrhage , fibrin exudation , fibrosis , hyalinization , and neovascularization . 
 ct and mri show heterogeneous findings reflecting a mixture of these pathological entities .