A Rare Case of Incidental Primary Follicular Lymphoma Co-Existing With Grade Group 5 Prostatic Adenocarcinoma

Abstract

Abstract Introduction/Objective Primary lymphoma of the prostate is an exceedingly rare entity comprising less than 0.1% of all prostatic cancers with follicular lymphoma making up only 12% of primary prostatic lymphomas. There is very limited literature owing to their rarity and underdiagnosis. To the best of our knowledge, prostatic adenocarcinoma with an incidental follicular lymphoma presenting as a prostate imaging reporting and data system 4 (PI-RADS 4) lesion on multiparametric magnetic resonance imaging (mpMRI) with mildly elevated serum prostate specific antigen (PSA) has not been previously described. Methods/Case Report A 73 year old male presented to Danbury Hospital for follow up on benign prostatic hyperplasia (BPH) diagnosed in 2020. The patient was experiencing nocturia and had a serum PSA of 4.8. Multiparametric MRI revealed an enlarged, 5.5 x 4.1 x 3.3 cm, prostate gland (estimate weight of 45.5 grams) with a 1.2 cm PI-RADS 4 lesion in the right anterior mid gland. There was no evidence of metastatic disease on his most recent body imaging. He was subsequently scheduled for prostate needle biopsy. Histopathology showed a high grade prostatic adenocarcinoma, with a Gleason score 4 + 5=9, along with a focally prominent dense lymphoid infiltrate in four of four cores from the same area of abnormality that was detected on mpMRI. The latter comprised of ill defined follicles and sheets of small cleaved atypical lymphoid cells consistent with centrocytes and very few centroblasts. By immunohistochemical staining, the atypical cells in lymphoid follicles and interfollicular areas were positive for CD20, CD10 and BCL2 and negative for cyclin D1. CD21 stain highlighted the follicular dendritic cell meshwork in the germinal centers with a low Ki67 proliferation index. A final diagnosis of low grade follicular lymphoma (grade1-2) coexisting with the prostatic adenocarcinoma was rendered. The patient is currently undergoing lymphoma staging as the treatment for adenocarcinoma is planned. Results (if a Case Study enter NA) NA Conclusion Primary lymphoma of the prostate usually presents with non specific obstructive voiding symptoms and normal or near normal PSA levels which makes it challenging for physicians to suspect lymphomas. The lymphocytic infiltrate, originally thought to be prostatitis, underwent further evaluation with immunohistochemistry due to its monotonous appearance, which clinched the final diagnosis. Careful evaluation of prostate core needle biopsies is necessary even after spotting carcinoma in order to rule out low grade lymphomas.