Background: Anal cancer in increasing in incidence in the United States, and a number of risk factors can predict the impact of treatment. The presence of macrophages as well as other inflammatory cells has been noted in many tumors, with the number and density of inflammatory cells predictive of metastasis and survival in some patients. Recruitment and infiltration of TAMs within the tumor microenvironment activates them, with subsequent support for malignant progression of epithelial cells, including release of pro-angiogenic factors, metalloproteinases, reactive oxygen species, and triggering of NFkB activation. TAMs have not been studied in anal cancer. Here we evaluated and quantified the presence of TAMs in a retrospective cohort of anal cancer cases to see it correlated with epidemiological information.Methods: Paraffin-embedded formalin-fixed tissue from ten cases of pathologically-confirmed squamous cell carcinoma of the anus were acquired from two local hospitals. Sections were immunohistochemically stained with antibody to CD68, a macrophage marker. CD68 positive cells were counted on a grid overlay of photomicrographs taken at 40X magnification, with only intratumoral TAMs contributing to the final count (i.e. no stromal macrophages counted). The TAM data was then correlated with clinical data that was previously obtained from the medical and pathological records.Results: The average age in our cohort of anal cancers was 52 years old with 60% men and 40% HIV positive. All cases were positive for HPV as determined by DNA sequencing. The mean number of intratumoral TAMs observed was 25.4 cells at 40X magnification (range 7.95-50.2). Less than 1 cell per 40X magnification was seen in the peritumoral and normal tissue. Forty percent of anal cancers at the time of diagnosis were stage 1, 30% were stage 2, 20% were stage 3, and 10% were stage 4. There was no association of TAM quantification with age, gender, HIV, HPV or smoking status. A higher number of TAMs were seen in advanced anal cancer cases (stage 3-4), with a mean of 35.6 intratumoral TAMs versus early staged anal cancers (stage 1-2) with a mean of 20.5 intratumoral TAMs at 40X magnification, although this approached but did not reach statistical significance (p=0.121).Conclusion: Anal carcinomas contain a higher number of intratumoral TAMs when compared to the surrounding peritumoral and normal tissue. We observed a trend towards higher numbers of TAMs in advanced cases of anal cancer when compared to early staged cases. The presence of macrophages within the tumors may be important in the progression of disease and pathogenesis, and this should be evaluated in a larger cohort.