Expression of alpha-methylacyl coenzyme A racemase in partial and complete focal atrophy on prostate needle biopsies.

OBJECTIVE

To describe the behavior of alpha-methylacyl coenzyme A racemase (AMACR) in focal atrophy including all subtypes. Focal prostatic atrophy is the benign lesion that most frequently mimicks adenocarcinoma particularly the partial variant.

STUDY

DESIGN

We analyzed the immunohistochemical expression of AMACR in normal glands and acini of adenocarcinoma, partial atrophy and all variants of complete atrophy of a total of 1,198 acini on needle prostatic biopsies.

RESULTS

Partial atrophy showed negative and weak expression of AMACR in 143/190 (75.3%), and 47/190 (24.7%) acini, respectively. The secretory (luminal) compartment in all variants of complete atrophy showed aberrant immunohistochemical expression: AMACR negative, prostate-specific antigen negative and 34betaE12 positive, suggesting an intermediate phenotype for these cells.

CONCLUSION

No strong positivity was seen in partial atrophy; however, the absence of basal cells in 23.2% acini of partial atrophy and the weak positivity seen in 24.7% acini that overlaps with 22.5% acini with weak expression in adenocarcinoma may be a pitfall for the correct interpretation in the differential diagnosis of cancer. Recognizing the hematoxylin-eosin features of partial atrophy is still the most critical aspect in preventing a misdiagnosis of adenocarcinoma.