Increased prostate-type acid phosphatase activity in serum and typical bone lesions simulating the presence of prostatic carcinoma.

In a man with myelomonocytic leukemia, the association of increased prostatic acid phosphatase activity in serum and the presence of typical bone lesions on roentgenography suggested the existence of disseminated prostatic carcinoma. During the clinical observation period, however, prostatic involvement could not be proved. Moreover, bone pain and prostatic-type acid phosphatase activity in serum closely paralleled monocyte counts and the degree of hepatosplenomegaly and leukemic skin lesions. Finally, meticulous postmortem examination of the prostate showed no prostatic carcinoma. This clinical picture appears to be entirely explicable in terms of leukemic organ infiltration and the proliferation of monocytes, which are known to contain acid phosphatase isoenzymes like those in the prostate.