Severe Xanthogranulomatous prostatitis mimicking prostate cancer: a case report

Abstract

Background

Xanthogranulomatous prostatitis is a rare, noncancerous inflammatory condition of the prostate that clinically resembles prostatic carcinoma, necessitating a pathological examination for accurate diagnosis.

Case presentation

A 75-year-old Egyptian male presented with urinary symptoms and an elevated serum prostate-specific antigen. Initial clinical and imaging findings suggested a locally advanced carcinoma of the prostate. However, histopathological examination after transurethral resection of the prostate revealed severe xanthogranulomatous prostatitis on a background of benign prostatic hyperplasia.

Conclusion

Xanthogranulomatous prostatitis can present with symptoms and radiological findings and biochemical markers similar to those of prostatic carcinoma. Accurate diagnosis of xanthogranulomatous prostatitis requires a high level of suspicion and close collaboration with a pathologist.

Background

Granulomatous prostatitis is an inflammatory condition affecting the prostate, characterized histologically by the presence of granulomas. The Epstein and Hutchins classification of granulomatous prostatitis is controversial, but commonly used; it divides it into four types: nonspecific (idiopathic), specific (infectious), iatrogenic, and secondary to systemic granulomatous diseases [1].

Xanthogranulomatous prostatitis (XGP) is considered a form of nonspecific prostatitis [2]. Only a limited number of cases have been documented in medical literature to date [2,3,4,5,6,7,8,9] (Table 1). XGP can be an incidental finding during or after a transurethral resection of the prostate (TURP). However, in some cases, XGP may clinically, biochemically, and even histologically, resemble prostatic malignancy, leading to potential diagnostic challenges [2]. Differentiation of these diseases is vital to offer the correct treatment. Histological examination of prostate tissue is the definitive manner in which XGP is distinguished from prostate cancer. Histologically, XGP is characterized by the presence of pale-appearing, lipid-laden macrophages, also known as foamy macrophages [3].

Table 1 Summary for previously published cases of xanthogranulomatous prostatitis

Among the novel immunohistochemical (IHC) markers that can differentiate between malignant and benign prostatic lesions are trophoblast cell surface antigen 2 (TROP2) and nuceophosmin. TROP2 is a trans-membrane glycoprotein, it has stem cell characteristics, it is normally expressed in basal layer of prostatic acini and is thought to show higher diffuse expression in prostatic carcinomas [10, 11]. Nucleophosmin is a nucleolar protein, has a role in cell cycle activation and promotes tumor growth. It has moderate expression in both basal and luminal layers of normal prostatic acini, in contrast with its stronger expression in malignant prostatic acini [12].

In this case report, we presented the findings of a case of XGP that was clinically and radiologically suspected to be prostatic cancer. In addition, we summarized the findings of previous published studies about XGP and highlighted the importance of the use of IHC markers, especially TROP2 and nucleophosmin, in confirming the inflammatory nature of the prostatic lesion of this patient.

Case presentation

A 75-year-old Egyptian male patient presented at the urology clinic, Suez Canal University Hospital, with a 4-month history of increased urinary frequency, difficulty in micturition, weak urine flow, and intermittency. There was no relevant past medical or family history. General examination of the patient revealed a male patient, of weight 80 kg and height 170 cm, with normal vital signs. General examination revealed no significant findings apart from a slightly tender pubic region. Digital rectal examination revealed an enlarged, hard, nodular, nontender prostate. His serum prostate-specific antigen (PSA) was 90 ng/ml. Transrectal ultrasound (TRUS) of the prostate gland showed prostatic enlargement, with an approximate weight of 70 g, and suspicious hypoechoic areas, leading to a clinical suspicion of locally advanced carcinoma of the prostate. TRUS biopsy specimens were obtained from different zones of the prostate and from the suspicious foci. The excised cores were fixed in 10% formalin and embedded in paraffin blocks. Serial sections, 5 µm thick, were processed for hematoxylin and eosin (HE) staining.

Histopathological examination of the resected prostatic cores revealed a nonspecific granulomatous inflammation centered mainly around ruptured or distended acini (Fig. 1A) and composed of abundant plasma cells (Fig. 1B), lymphocytes, neutrophils, eosinophils, and scattered few multinucleated giant (MNG) cells. There were sheets of large cells with abundant clear to foamy cytoplasm and eccentric atypical nuclei, that raised the suspicion of signet ring-like cell adenocarcinoma (Fig. 1B). We thus performed a set of immunohistochemical (IHC) staining markers (Table 2) to rule out malignancy. Primary antibodies (Table 2) were purchased from Cell signaling (Danvers, MA, USA) and Thermo Fisher Scientific (Waltham, MA, USA).

Fig. 1

Representative histopathological figures for hematoxylin and eosin stained sections from prostatic cores. A There was dense granulomatous inflammation (black arrows), centered mainly around ruptured or distended acini (black arrowheads) (hematoxylin and eosin, 200×). B Higher magnification of the previous figure shows abundant plasma cells (red arrows) in the inflammatory foci, together with lymphocytes, macrophages, and neutrophils. There are foamy cells with abundant clear cytoplasm and eccentric atypical nuclei (red arrowheads), imparting a signet-ring like appearance (hematoxylin and eosin, 400×)

Table 2 Antibodies used for immunohistochemistry (IHC). Lot and working dilutions of antibodies are indicated

The cells stained positive for LCA and CD68 and were negative to PanCK, confirming their inflammatory phenotype and excluding an epithelial neoplasm. Moreover, prostatic acini showed positive staining of basal layer of prostatic acini by TROP2 and moderate expression of neucleophosmin staining both basal and luminal layers of prostatic acini, confirming their benign non-neoplastic nature (Fig. 2). Auramine-rhodamine and Grocott–Gomori’s methamine silver stains were negative for acid-fast bacilli and fungi, respectively. The final diagnosis was severe xanthogranulomatous prostatitis on a background of benign prostatic hyperplasia.

Fig. 2

Representative immunohistochemical stained figures for prostatic tissue by LCA, CD68, PanCK, TROP2, and nucleophosmin. The inflammatory cells show positive reaction to LCA and CD68 (black arrows). Foamy cells stain negative to PanCK (arrow heads). The prostatic acini showed positive TROP2 staining of only basal layer (red arrows), while the surrounding stromal cells and inflammatory infiltrate were negative. The reaction to nucleophosmin was positive in both basal and luminal cells of prostatic acini (red arrows), with similar intensity of the surrounding inflammatory infiltrate (black arrows) (immunohistochemical, 200×)

Owing to severe obstructive urinary symptoms, a transurethral resection of the prostate (TURP) was performed. Histopathological examination of the resected prostatic tissue confirmed xanthogranulomatous prostatitis with no evidence of malignancy. The patient remains symptom-free at a 12-month follow-up, and his serum PSA has decreased to 4.5 ng/ml.

Discussion and conclusion

Xanthogranulomatous prostatitis (XGP) is considered a form of nonspecific prostatitis [2]. It is usually a diffuse process, characterized by poorly defined, expansile nodular infiltrates, usually involving the entire lobules, formed of marked chronic inflammation, fibrosis, and granulomas showing epithelioid histiocytes, lymphocytes, and plasma cells. Also, mild reactive cytological atypia in prostatic acini could be observed in some cases [2].

In this study, the patient was presented with elevated serum prostate-specific antigen (PSA) and enlarged, hard, nodular nontender prostate, which showed hypoechoic areas by transrectal ultrasound (TRUS), which led to the clinical suspicion of locally advanced carcinoma of the prostate, as previously observed in some cases [3, 7].

Pathologically examined tissue cores obtained from the patient’s prostate showed a nonspecific chronic granulomatous inflammation centered mainly around ruptured or distended acini, with aggregates of large cells with abundant clear to foamy cytoplasm and eccentric atypical nuclei, that raised the suspicion of signet ring-like cell adenocarcinoma, similar to previously reported cases [7, 13].

Immunohistochemical (IHC) analysis was thus performed to ensure its benign nature and exclude any underlying associated malignancy. Stromal cells and associated epithelioid inflammatory cells showed positive expression for LCA and CD68 and were negative to PanCK, which confirmed the inflammatory nature of the lesion [14].

The use of IHC markers TROP2 and nucleophosmin was also performed, for confirmation of the benign nature of the lesion. The prostatic acini showed positive TROP2 staining of only basal layer, while the surrounding stromal cells and inflammatory infiltrate were negative for TROP2, this is in keeping with the pattern of TROP2 expression in benign prostatic lesions, in contrary to its stronger diffuse staining in the malignant lesion [11].

Moreover, in our patient, the prostatic acini showed moderate expression of neucleophosmin staining of both basal and luminal cells, with similar intensity of the surrounding inflammatory infiltrate and stromal tissue, and with no expression in the suspicious large cells. Such pattern of expression is typical of that of benign prostatic [12].

Following TURP, and prior to discharge, NSAIDs (oral diclofenac potassium of 50 mg twice a day) and antibiotics (oral Ciprofloxacin of 500 mg twice a day) for 5 days were prescribed. The patient showed marked improvement of his symptoms with significant decline in his serum PSA level over a follow up period of 2 months at the urology outpatient clinic, Suez Canal University Hospital.

Conclusion

XGP is a rare chronic nonspecific prostatitis that has clinical, radiological, and histopathological features mimicking some types of prostatic carcinoma. Clinical and radiological correlation, careful microscopic examination, and even immunohistochemical staining could be useful to rule out associated malignancies for proper treatment plan and for avoiding unnecessary procedures.