A major solid undifferentiated carcinoma pattern correlates with tumour progression in locally advanced prostatic carcinoma.

Solid undifferentiated carcinoma was the major microscopic pattern in 24 prostatic carcinomas, 12 of which were clinically recurrent. Tumour cells were uniform, with moderately hyperchromatic nuclei and indistinct cytoplasm, and were arranged in solid or focally irregular aggregates. In areas, the tumour cells were large with vesicular nuclei, nucleoli and more abundant cytoplasm. In previous specimens, solid undifferentiated carcinoma was absent or was a minor pattern. Twenty of 23 cases showed prostate specific antigen and prostatic acid phosphatase immunoreactivity, and nine of 17 cases contained scattered argyrophilic or chromogranin-immunoreactive cells. On proliferating cell nuclear antigen immunostaining of 12 specimens, the mean tumour proliferative fraction in solid undifferentiated carcinoma (range: 10.5-18%) was greater than in areas of grade 3 prostatic carcinoma (range: 3-6%). In all 22 stage C and D cases, there was a close correlation with clinical evidence of tumour progression, and the overall 2-year survival rate was only 16.7%. It is concluded that a major solid undifferentiated pattern correlates with increased biological aggressiveness and a poor prognosis in locally advanced prostatic carcinoma.