Spindle cell squamous carcinoma of the esophagus: analysis of ploidy and tumor proliferative activity in a series of 13 cases.

Spindle cell squamous esophageal carcinomas are distinctive polypoid "biphasic" tumors in which the sarcoma-like phenotype usually predominates over the epithelial component. To biologically assess both phenotypes, we compared the tumoral proliferative activity and DNA ploidy between the two histological components of 13 polypoid spindle cell squamous carcinomas of the esophagus. We studied the tumoral proliferative index (TPI) using MIB 1 monoclonal antibody (Ki-67) and determined the DNA histogram by image cytometry on Feulgen-stained sections. The DNA histograms were classified into four types (I to IV) according to the degree of dispersion of the DNA. The TPI of the carcinomatous regions ranged from 0.20 to 0.63 (mean, 0.44) and from 0.55 to 0.85 for the sarcoma-like areas (mean, 0.68) P < .0001. In all cases, the sarcoma-like areas were aneuploid, and 37.5% of the carcinomatous regions were diploid. Also, in all instances the carcinomatous areas were of either histogram type I or II, and the sarcoma-like areas showed histograms of type II or III. We conclude that in esophageal spindle cell squamous carcinomas the sarcoma-like phenotype differs biologically in two ways from the carcinomatous: (1) it has a higher TPI and (2) it has higher aneuploidy with a greater dispersion of the DNA content. We postulate that these characteristics could give a "growth" advantage to the sarcoma-like component of these tumors and explain its predominance over the carcinomatous component.