carcinoma of the gallbladder is more common in women and usually seen in patients older than 50 years of age .
it is more common in the white population than the black and in western countries than the mediterranean .
although areas of squamous differentiation is seen in adenocarcinoma , pure primary squamous cell carcinoma is rarely reported and accounts for less than 1% of all gallbladder malignancies .
some researchers have stated that squamous cell carcinoma originates from pre - existing squamous metaplasia of the gallbladder epithelium , while others concluded that it originates from squamous differentiation of neoplastic cells of adenocarcinoma .
we present a pure case of squamous cell carcinoma with some areas of squamous metaplasia in the vicinity of the invasive tumor .
another purpose of this case presentation was to emphasize on the vague clinical presentation of gallbladder carcinoma .
a 70-year - old man presented with acute onset right upper quadrant abdominal pain and fever since two days prior to admission .
liver function tests showed total protein : 7.2 g / dl , alb : 4.1 g / dl , alt:40 iu , ast : 38 iu , alkaline phosphatase : 150 iu , total bilirubin : 2.3 mg / dl , and direct bilirubin : 1.8 mg / dl .
abdominal ultrasonography showed thickened gallbladder wall without gallstone in favor of acute acalculus cholecystitis . with the presumptive diagnosis of acute cholecystitis , the patient received supportive care and antibiotics .
gross examination of the gallbladder revealed an ill - defined infiltrating creamy white mass in the body of the gallbladder measuring 322 cm with focal exophytic configurations ( figure 1 ) .  
gross appearance of the squamous cell carcinoma shows the infiltrative tumor and a focal fungating configuration .
microscopic examination of the mass showed well differentiated keratinized squamous cell carcinoma invading full wall thickness to the serosal surface ( figures 2 and 3 ) .
the mucosa showed mature squamous metaplasia in the vicinity of the tumor ( figure 4 ) .
the tumor lacked any glandular differentiation . in the follow - up visits all examinations were negative for the primary origin of the squamous cell carcinoma and the patient was well in a follow - up period of 6 months .
this figure shows well differentiated keratinized squamous cell carcinoma is invading through the wall of the gallbladder ( h&e100 ) .
this figure shows areas of extensive keratinization is shown in invasive squamous cell carcinoma ( h&e400 ) .
this figure shows mature squamous metaplasia of the gallbladder mucosa is shown in the vicinity of the tumor ( h&e400 ) .
adenocarcinoma is the most common histological subtype of gallbladder cancer constituting about 90 - 95% of the cases .
although areas of squamous differentiation are seen in some reported cases , pure squamous cell carcinoma of the gallbladder is very rare .
traditionally it has been said that adenosquamous and squamous cell carcinomas have very poor prognosis . however , currently it is important to differentiate adenocarcinoma with squamous differentiation from pure squamous cell carcinoma because of the better prognosis of the latter .  
pure squamous cell carcinoma of the gallbladder grows slowly , is usually localized and rarely metastasized . on the other hand adenosquamous carcinoma is aggressive and metastasizes widely .
the mean age of the patients with squamous cell carcinoma was 65 years and only 13% of patients were suspected for carcinoma preoperatively .
the etiology and pathogenesis of squamous cell carcinoma is not well understood ; however , two important presumptive causative possibilities are gallstones and parasitic infestation .
another important pathogenetic clue for squamous cell carcinoma is the metaplasia - dysplasia - carcinoma sequence .
most of the cases with squamous cell carcinoma show some degrees of atypical epithelial change adjacent to the invasive tumor .
gupta and co - workers reported a case of primary squamous cell carcinoma presenting as acute cholecystitis .
the patient was operated on after 12 hours and cholecystectomy showed wall thickening with multiple gallstones .
other researchers reported a case of primary squamous cell carcinoma of the gallbladder in an elderly lady with infiltration to the adjacent hepatic parenchyma .
rai and colleagues concluded that pure squamous cell carcinoma of the gallbladder was less aggressive than adenocarcinoma .
this type of carcinoma should be suspected when the lesion reaches a large size without metastasis .
we presented a 70-year - old man diagnosed as having acute cholecystitis based on clinical examinations and ultrasonographic findings .
in our case the subtle clinical presentation could be in favor of the less aggressive behavior of pure squamous cell carcinoma of the gallbladder in comparison with adenocarcinoma or adenosquamous variants , which was reported in some previous studies .
 squamous cell carcinoma of the gallbladder is rare and constitutes only 0.5 - 3% of all malignancies of this organ . 
 most of the reported cases have had a component of adenocarcinoma . 
 we report a 70-year - old man who presented with acute onset right upper quadrant pain . 
 he operated on based on a presumptive diagnosis of acute cholecystitis according to clinical and ultrasonographic findings . 
 histopathological examination of the infiltrating mass of the gallbladder revealed well differentiated keratinized squamous cell carcinoma invading full wall thickness . 
 thorough evaluations revealed no other primary site for the tumor . 
 pure primary squamous cell carcinoma of the gallbladder is rarely reported . 
 clinicians and pathologists must be aware of its vague clinical presentations . 
Introduction
Case Description
Discussion
Conclusion
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