In the United States, esophageal squamous cell carcinoma typically occurs in adults older than 45 years of age and affects males four times more frequently than females. Risk factors include alcohol and tobacco use, poverty, caustic esophageal injury, achalasia, Plummer-Vinson syndrome, frequent consumption of very hot beverages, and previous radiation therapy to the mediastinum. It is nearly six times more common in African Americans than in whites—a striking risk disparity that cannot be accounted for by differences in rates of alcohol and tobacco use. The incidence of esophageal squamous cell carcinoma can vary by more than 100-fold between and within countries, being more common in rural and underdeveloped areas. The countries with highest incidences are Iran, central China, Hong Kong, Argentina, Brazil, and South Africa.
A majority of esophageal squamous cell carcinomas in Europe and the United States are at least partially http://ebooksmedicine.net related to the use of alcohol and tobacco, the effects of which synergize to increase risk. However, esophageal squamous cell carcinoma also is common in some regions where alcohol and tobacco use are uncommon due to religious or societal norms. In these areas, nutritional deficiencies, as well as exposure to polycyclic hydrocarbons, nitrosamines, and other mutagenic compounds, such as those found in fungus-contaminated foods, are suspected to be the risk factors. HPV infection also has been implicated in esophageal squamous cell carcinoma in high-risk but not in low-risk regions. The molecular pathogenesis of esophageal squamous cell carcinoma remains incompletely defined.
MORPHOLOGYIncontrasttothedistallocationofmostadenocarcinomas,halfofsquamouscellcarcinomasoccurinthemiddlethirdoftheesophagus(
Fig.15.12A ).Squamouscellcarcinomabeginsasaninsitulesionintheformofsquamous dysplasia. Earlylesionsappearassmall,gray-whiteplaquelikethickenings.Overmonthstoyears,theygrowintotumormassesthatmaybepolypoidandprotrudeintoandobstructthelumen.Othertumorsareeitherulceratedordiffuselyinfiltrativelesionsthatspreadwithintheesophagealwall,wheretheycancausethickening,rigidity,andluminalnarrowing.Thesecancersmayinvadesurroundingstructuresincludingtherespiratorytree,causingpneumonia;theaorta,causingcatastrophicexsanguination;orthemediastinumandpericardium.
Fig. 15.12 Esophagealsquamouscellcarcinoma.(A)Squamouscellcarcinomamostfrequentlyisfoundinthemid-esophagus,whereitcommonlycausesstrictures.(B)Squamouscellcarcinomacomposedofnestsofmalignantcellsthatpartiallyrecapitulatethestratifiedorganizationofsquamousepithelium.
Fig.15.12B ).Regardlessofthehistologysymptomatictumorshaveofteninvadedtheesophagealwallattimeofdiagnosis.Therichsubmucosallymphaticnetworkpromotescircumferentialandlongitudinalspread,andintramuraltumornodulesmaybepresentseveralcentimetersawayfromthemainmass.Thesitesoflymphnodemetastasesvarywithtumorlocation:Cancersintheupperthirdoftheesophagusfavorcervicallymphnodes;thoseinthemiddlethirdfavormediastinal,paratracheal,andtracheobronchialnodes;andthoseinthelowerthirdspreadtogastricandceliacnodes.