Adenosquamous Carcinoma of the Gallbladder: A Clinicopathological, Immunohistochemical and Flow‐cytometric Study of Twenty Cases

Twenty patients (7.4%) with adenosquamous carcinoma of the gallbladder were selected from 271 surgically resected gallbladder cancers. The 20 patients were composed of 8 men and 12 women with a mean age of 66.9 years. Histologically, all twenty tumors showed an abrupt transition between the adenocarcinoma (AC) and squamous cell carcinoma (SCC) areas, and well differentiated AC was also found in the peripheral area of the tumor. A histochemical and immunohistochemical study using alcian blue, periodic acid‐Schiff, cytokeratins, involculin and tissue polypeptide antigen disclosed a different nature of the two components. DNA heterogeneity between the components was detected in 5 of 7 cases by flow cytometry. The positive rate of immunostaining for proliferating cell nuclear antigen in the SCC areas (mean 20.55%) was larger than that of the AC areas (mean 11.40%) (P=0.0029), which indicated that the SCC areas had a greater proliferative capacity than AC areas. These results suggest that the SCC component of adenosquamous carcinoma of the gallbladder arose by a stepwise molecular progression of the pre‐existing AC. Furthermore, the prognosis of adenosquamous carcinomas of the gallbladder (mean survival: 10 months) in the advanced stage (pTNM 2–4) was less favorable than those of papillary and well differentiated AC (mean survival: 99 months and 86 months) (p<0.0001).