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 .