The diagnostic value of fine needle aspiration cytology for prostate lesions at muhimbili national hospital

Abstract

This crossectional descriptive study was designed to determine the diagnostic value

of FNAC, as compared to Tm Cut biopsy, a method considered as the gold standard

for tissue diagnosis for prostate lesions at MNH~

Patients suspected to have cancer of the prostate from abnormal DRE such as

nodular, hard, irregular enlarged prostate or from high levels of PSA (4.Ong/ml or

more) or from ultrasonography of hypo echoic lesion(s) or having any combination

of the three, were included after their voluntary consent had been obtained. They

had both FNAC and Tm Cut biopsies performed at the same sitting, FNAC preceded

Tm Cut biopsy always. Smears made at FNAC were fixed in 95% alcohol while the

core biopsy specimens were preserved in formalin, and both were labeled and

submitted to the pathology laboratory. A specific cytologist was given FNAC

specimen to interpret while histology specimen where sent to other pathologists so as

to avoid bias at reporting results.

A total of 119 patients met the inclusion criteria for the study between first date of

March and the last date of December 2006. One hundreds and ten patients (92%)

enrolled into the study had PSA levels more than 4 ng/ml ,thirty two patients enrolled

had hypo echoic lesion at ultrasonography and of the enrolled patients grade three

prostate enlargement was found in 76(63.9%). Cancer was diagnosed by histology in

57(47.9%) patients as compared to 50(42%) cancer diagnoses by cytology. The age

most commonly affected by cancer when the gold standard (core needle) biopsy

when used was 60-69 years. Cancer of prostate was uncommon in patients below 60 years.The accuracy of FNAC diagnosis for prostate lesions when compared with

histological diagnosis as standard test was calculated from 101 patients who had

adequate specimens for comparison. A total of 18 patients had inadequate specimen

of which 11 had inadequate cytology and 7 had inadequate histology were not

included at calculating the accuracy. Thirty eight cases were found to have True

Positive (TP) cancer diagnoses , 41 patients had True Negative (TN) results,12

patients had false negative (FN)results and 10 patients had False positive (FP)results

for prostate cancer diagnosis .The sensitivity of FNAC was found to be 76%,

specificity of FNAC was 80.3%, positive predictive value (PPV) was 79.2%,

negative predictive value (NPV) of FNAC was 77.4% and the overall accuracy of

FNAC in study was 78.2%

The use of FNAC had an overall cost reduction of more than 77.5% of the cost core

needle biopsy. When under optimal conditions FNAC would minimize the duration

to obtain tissue diagnosis results for about 97% of the duration required for

histology diagnosis .The fact that some prostate cancer patients are severely anemic,

therefore a more invasive procedure such as core biopsy would worsen the pre

existing anemia, this may be avoided by using FNAC instead

Fine needle aspiration of the prostate should be introduced at MNH and prostate

aspiration procedures should be part of training for medical doctors in surgery and

histopathology. Also systematic sampling of the prostate should also be introduced

so as to increase the diagnostic accuracy of core needle biopsy.