solitary necrotic nodule ( snn ) of the liver is a rare benign lesion first reported in 1983 by shepherd and lee , who described four lesions with a completely necrotic core and a hyalinized fibrotic capsule containing elastic fibers . to date , fewer than 60 cases have been reported .
koea et al . , in a revision of the literature performed up to 2003 , reported only 50 cases , the majority of which were found in males and over three - quarters in the right lobe of the liver .
we here report a patient who underwent laparoscopic cholecystectomy for multiple lithiasis and who was accidentally found to have a snn of 2 cm in the fifth segment of the liver , which had not been observed on previous ultrasound ( us ) . on the basis of the histological findings
, we discuss the various hypotheses regarding the histogenesis of this rare lesion , which is still debated .
furthermore , this is the first case of laparoscopic resection of this uncommon benign liver lesion .
a 58-year - old woman was admitted to our ward following a history of several episodes of cramp - like pains in the right hypochondria irradiating to the ipsilateral scapula in the previous six months . on admission ,
us of the upper abdomen showed multiple stones in the gallbladder without any lesion of the liver .
, a single round lesion of 2 cm located on the edge of the fifth liver segment , about 2 cm from the bottom of the gallbladder , was found .
the macroscopic finding of the resected specimen showed the presence of a lobular - shaped formation with a hard consistency .
extemporary histological examination performed on the liver mass showed a picture of tissue necrosis alone .
the definitive histological examination on hematoxylin - eosin stained sections revealed a nodule with a completely necrotic core , combined with eosinophil granular matter , calcifications , cholesterol , foam cells , and some inflammatory cells .
shikata 's orcein staining showed the presence of elastic fibers in the capsule , but not in the central necrotic core ( fig .
on the other hand , the central necrotic core stained deeply for gomori 's silver stain , showing the collapse of the reticular fibers ( fig .
after surgery , plasma levels of some tumor markers such as cea , ca 19 - 9 and alpha - fetoprotein were normal .
systemic examinations were performed to investigate the possibility of metastasis from the digestive tract or gynecological malignancy , but no abnormal findings were found on ct study .
clinical and instrumental controls performed up to 1 year after surgery showed no signs of disease or recurrence , and the patient is in good health .
snn of the liver is a rare benign lesion ; to date fewer than 60 cases have been reported in the literature .
reported one case taken from 500 referrals with liver masses presenting over a 2-year period , berry   reported 2 lesions in 1,000 post mortems and tsui et al .  
most of the reported cases have been in males and the majority have been seen in the seventh and eighth decades of life .
however , a number of cases have been found in patients in their thirties and forties [ 5 , 6 , 7 , 8 ] , whereas tsui et al . reported a case of a patient as young as 27 years old .
three - quarters of these rare benign lesions occurred in the right lobe of the liver . in the initial description by shepherd and lee
, all snns were reported on the surface of the liver and most of them were located on the right side , probably because the right lobe of the liver is easy to examine , but also because of the possibility that trauma may be involved in the pathogenesis of these lesions .
only four of the reported snns were found in the left lobe [ 1 , 4 ] . in a review of 21 cases performed by imura et al . , it was noted that in fifteen cases the tumor was 2.0 cm in diameter and that all the lesions were < 5.0 cm ; only in one case did the authors find a mass 8.5 cm in diameter . in the literature , there is a reported association with tumor pathology in > 50% of cases . this kind of lesion is normally accidentally diagnosed during a workup for other pathologies or is an occasional finding during abdominal surgery or autopsy . in the majority of cases ,
this condition is clinically silent , and often the patients complain of nonspecific and unclear symptoms .
some features , such as lobular shape , well - delineated margin , and close proximity to the hepatic inflow structures , are suggestive of snn , but are nondiagnostic .
since conventional color / power doppler imaging is insensitive to the slow flow of deep - seated blood vessels , the lack of blood flow signal can not confirm a total absence of blood perfusion within the lesion .
snn usually appears as a well - defined lesion with no enhancement on contrast ct or mri   or us , while some snns may have subtle peripheral enhancement on contrast mri .
often the radiological findings of snn of the liver are similar to those of hepatic metastasis or other liver masses , such as pseudotumor , lymphoma , regenerative and dysplastic nodules , or some infectious processes . due to these similar radiological findings , making a correct differential diagnosis is often very difficult or impossible .
the intraoperative us findings of the lesion also simulate hepatic metastasis , even though lesion multiplicity had been elucidated .
furthermore , the cytological evaluation of specimens obtained by needle biopsy is not useful to correctly distinguish between these nodules and hepatic metastasis , because it often reveals only the presence of necrotic tissue . due to these difficulties , performing a liver biopsy in order to clarify
, snn appears well - delineated by a dense fibrohyalinized fibrotic capsule with a principally necrotic core containing an eosinophil granular matter combined with calcifications , cholesterol , foam cells , and some inflammatory cells .
characteristically ziehl - neelsen , gram and pas stains do not reveal bacteria or fungi , and the pathogenesis of these cases remains uncertain . the histological findings of our case were in keeping with the above - mentioned features .
the etiology of these rare benign lesions is still uncertain ; at least three different hypotheses have been suggested as to their origin .
some authors argue that these nodules have a traumatic etiology or that they are the result of previous parasitic infestation [ 1 , 4 , 5 ] .
others suggest that because of the finding of a  feeding vessel and the absence of a cystic space or other signs of parasitic infestation , the lesions could be the result of the sclerotic evolution of small hemangiomas [ 2 , 3 , 8 ] . finally , the possibility that a snn of the liver may develop by two or more different mechanisms can not be denied .
we agree with this last hypothesis that at least two different pathogenetic mechanisms could be involved .
to support this claim , we would like to show the histological differences between the case we report in this work and a previously observed case of ours ( unpublished ) . in the latter ,
furthermore , the central core was more fibrous than necrotic and shikata 's orcein staining , evidencing several circular - running elastic fibers , suggested the presence of sclerotic vessels ( fig .
2b ) with lumina occluded or reduced to a thin fissure , evidenced only by performing anti - cd31 , anti - cd34 and anti - factor viii immunostaining to highlight the presence of the endothelial cells ( fig .
finally , gomori 's silver staining did not show the collapse of the reticular network , but evidenced some reticular fibers around the vascular lumina ( fig .
consequently , we think that careful observation and special staining could be useful to highlight morphological differences in snn , which suggest the hypothesis of a different histogenetic origin . to our knowledge ,
de luca et al . in their report observed a reduction in size of snn during follow - up , whereas imura et al .
reported a case with rapid enlargement in diameter from 3 cm to > 8 cm in the space of seven months . in conclusion , although the benign behavior of this lesion and the absence of symptomatology suggest that surgical resection is unnecessary , the radiological suspicion of snn demands to perform a liver biopsy , and in case of failure , given the high association of snn with malignant lesions , confirms resection as the treatment of choice in the management of this disease .
 solitary necrotic nodule of the liver is a rare benign lesion the histogenesis of which is still debated . 
 we here report the case of a patient who underwent laparoscopic cholecystectomy for gallstones and who was accidentally found to have a solitary necrotic nodule of 2 cm in the fifth segment of the liver . on the basis of the histological findings , the hypothesis that different pathogenetic mechanisms could be involved in the histogenesis of this lesion 
 is discussed . 
Introduction
Case Report
Discussion