COW-2020-36

CASE OF THE WEEK

2020-36 / September 7
Contributors: Maiara Ferreira de Souza, Diogo Diniz, Daniel Athanazio

A male patient in his 70s underwent prostatectomy 3 months after 12-core prostate biopsy with the diagnosis of acinar adenocarcinoma Gleason 3+4 (Grade Group 2) in one biopsy site. The images are from the prostatectomy specimen.

Quiz

1. What is the correct grading?

a. Gleason 3 + 3 (Grade Group 1)

b. Gleason 3 + 4 (Grade Group 2)

c. Gleason 4 + 3 (Grade Group 3)

d. Gleason 3 + 5 (Grade Group 4)

e. Gleason 5 + 4 (Grade Group 5)

1. Gleason 3 + 4 (Grade Group 2)

Malakoplakia is a rare form of chronic inflammation characterized by solid and often extensive aggregates of foamy or eosinophilic epithelioid histiocytes. Figures 1,3 and 4 shows the transition of a small (unifocal) acinar adenocarcinoma to a solid area of malakoplakia. Figure 2 details areas of well differentiated (Gleason pattern 3) and poorly differentiated glands (Gleason pattern 4) from the acinar adenocarcinoma focus. Figure 5 shows PAS stain that enhances the cytoplasmatic inclusions in the solid lesion (while negative in the adenocarcinoma) and von Kossa stain highlighting Michaelis-Gutmann bodies with iron and calcium contents. Note that these inclusions could be readily recognized in the solid area of figure 4 (H&E stain).

Malakoplakia is a well-known mimicker of high grade (Gleason pattern 5) adenocarcinoma. In this case, proper recognition of this lesion avoided overgrading. The prostatectomy specimen confirmed the findings of a unifocal GG2 tumor from the needle biopsy. Since no inflammation or histiocytic lesion was seen in the biopsy samples, we may speculate that malakoplakia in this case could correspond to a complication secondary to infection after the biopsy procedure, as it has been described in rare cases in literature.

Srigley JR. Benign mimickers of prostatic adenocarcinoma. Mod Pathol. 2004;17(3):328-348.

Trpkov K. Benign mimics of prostatic adenocarcinoma. Mod Pathol. 2018;31(S1):S22-S46.

Medlicott S, Magi-Galluzzi C, Jimenez RE, Trpkov K. Malakoplakia associated with prostatic adenocarcinoma: Report of 4 cases and literature review. Ann Diagn Pathol. 2016;22:33-37.

Guner G, Akdogan B, Baydar DE. Malakoplakia of prostate as a complication of transrectal needle biopsy. Can J Urol. 2012;19(1):6124-6127.

Maiara Ferreira de Souza
Diogo Diniz
Daniel Athanazio
Imagepat, Laboratory of Pathology
Salvador, Bahia, Brazil

Prostate

Prostate; Prostate Neoplasms; Malakoplakia