There is only one other case report in the literature of a prostate MALT lymphoma with concurrent adenocarcinoma, in which the adenocarcinoma was treated according to the stage while the MALT lymphoma was managed according to individual treatment strategies.17
Because MALT lymphomas are characteristically indolent and prostatic adenocarcinomas are more aggressive in nature, therapy is targeted toward treating the adenocarcinoma. Unfortunately, the chronology in which the cancers appeared is unknown, but perhaps the difference in their prognoses may give insight into the etiology.
The long, indolent course of MALT lymphomas might suggest that the disease is the result of a chronic process. Typically, they arise in extranodal sites that lack native lymphoid tissue but acquire MALT in close association with chronic inflammation or autoimmune processes, like Sjogren's syndrome and chronic sclerosing sialadenitis.20
They arise most commonly in the stomach, orbit, thyroid, salivary glands, breast, lung, skin, and bladder. However, they have also been reported to occur in the gallbladder, nasopharynx, and thymus.21
MALT is known to develop in regions associated with infection or inflammation. Gastric MALT lymphoma is associated with H. pylori
cutaneous MALT is associated with Borrelia burgdorferi
infection in Europe but not in the United States, orbital adnexal MALT lymphoma is associated with Chlamydophila psittaci
, and intraocular MALT is associated with Toxoplasma gondii
Even though there have been specific infectious agents associated with MALT, not all MALT can be linked to a specific microbe. The genitourinary tract is part of the mucosal immune system, and includes prostate-associated lymphoid tissue (PALT). PALT consists of intra-epithelial leukocytes (mostly T-cells) and lymphoid aggregates below the epithelia, which constitute sufficient machinery for cellular and humoral immune responses.24
The PALT contains some native B-cells, and thus houses an entirely local prostatic source of progenitor cells for the development of MALT lymphoma.
There has been discussion in the literature that prostate MALT lymphoma may be associated with H. pylori
infection, but eradication of H. pylori
is not yet a standard treatment for MALT lymphoma of the prostate because the role of infection has not been validated.22
Previous case reports of urine cultures have been negative and often there is no history of acute prostatitis in patients with the disease.15,16
However, given the long history of urin ary obstruction in four out of six case reports and another with noted prostatism, chronic inflammation would seem likely to play a significant role in the etiology of MALT lymphoma of the prostate. The unique composition of the prostate provides a suitable environment for MALT to arise from normal prostate-associated lymphoid tissue. It is noted that prostate cancer and benign prostatic hyperplasia (BPH) can be associated with prostatitis. There are some investigators who hypothesize that inflammation may be linked to the development of prostate cancer. Pathological specimens from transurethral resection of the prostate (TURP) and radical prostectomy have been shown frequently to be associated with inflammation.25
Areas of inflammation show up the regulation of bcl-2.26
It is still unknown if BPH and prostate cancer promote or develop in response to inflammation. Thus it is difficult to assess if the two primary cancers occurred in a synchronous or metachronous fashion. Did chronic inflammation increase the risk of developing both prostate adenocarcinoma and MALT or did the prostate cancer create a local inflammatory environment more likely to induce MALT transformation from normal prostate-associated lymphoid tissue? MALT of the prostate is a rare entity and concurrent disease is even rarer. With such few cases reported in the literature, while there are millions of men diagnosed with BPH and prostate cancer annually, determining the sequence of events is likely impossible.
It has been difficult to establish the precise roles of infection (with one pathogen or multiple) versus inflammation in instigating MALT lymphoma of the prostate. MALT lymphomas may also arise from more than one clonegen adding even more complexity to the question of synchronous versus metachronous occurrence. 27,28
The prostate is a site with the potential for such transformation but this is rare. Nevertheless, this case shows that MALT lymph oma of the prostate can arise concurrently with adenocarcinoma of the prostate.