Clinicopathologic analysis of undifferentiated carcinoma of the gallbladder

Background: Undifferentiated carcinoma (UC) of the gallbladder (GB) is a rare malignant neoplasm and there have only been sparse case reports without precise description. We analyzed eight cases of UC of GB and compared with gallbladder carcinoma (GBC) in the aspects of clinicopathologic characteristics and prognosis.

Methods: We found eight UC cases out of 238 surgically resected GBCs. Patients with stage-matched GBC were selected (1:4) for comparative analysis of the clinicopathologic features and survival of UC.

Results: Histologically, UC cases were composed of four sarcomatoid, two pleomorphic, one small cell, and one osteoclast-like giant cell types. There was no difference between UC and ordinary GBC in clinicopathologic parameters, except for tumor size. It was significantly larger in UC (median; 5.0 cm, ranging 1.3-10.0 cm) compared to GBC (median; 3.0 cm, ranging 1.5-9.0 cm, P = 0.01). UC presented frequent intraluminal polypoid mass (87.5%: 7/8). UC showed significantly poor overall survival rate (37.5%, 37.5% and 18.8% at 1, 3, and 5 years), than GBC (84.4%, 65.6% and 52.1%, respectively) (P = 0.005). Pathologic findings of UC were an independent prognostic factor for poor survival in GBC (HR 7.242, 95% confidence interval: 1.799-29.147).

Conclusions: Undifferentiated carcinoma of the gallbladder was a rare highly malignant neoplasm and frequently presented a large intraluminal polypoid tumor. It showed a significantly larger tumor size and poorer survival than GBC.