Primary ALK-Negative TP63 -Rearranged Anaplastic Large Cell Lymphoma in the Bladder: Potential for Misdiagnosis

Introduction

Primary bladder lymphomas account for 0.2% of all bladder neoplasms and extranodal mucosal associated lymphoid tissue lymphoma is the most common subtype. ¹ Bladder involvement by lymphoma is usually asymptomatic but in rare circumstances symptomatic cases present with non-specific lower urinary tract symptoms that are indistinguishable from other bladder neoplasms.

There are currently at most fifteen cases of anaplastic large cell lymphoma (ALCL) involvement of the bladder reported in the literature, only one case was found to be a primary anaplastic lymphoma kinase positive (ALK-positive) ALCL. ² Of all the ALCL cases only three were found to be anaplastic lymphoma kinase negative (ALK-negative), two of which were diagnosed via cytology,^3–5 and all occurred secondary to disseminated disease. Our case represents the first case of primary ALK-negative ALCL involvement of the bladder in the literature to the best of our knowledge.

Report of a Case

A generally fit and well 76-year-old man presented to the emergency department post collapse. He had a history of persistent lower urinary tract symptoms of 4-week duration and was on his third course of oral antibiotics prescribed by the general practitioner for a presumed urinary tract infection. He was discovered to be in acute kidney injury with a creatinine of 1600 umol/L. Subsequent computed tomography showed bilateral hydronephrosis associated with markedly thickened bladder wall around the base. The initial impression was bilateral ureteric obstruction secondary to bladder cancer. He was then managed with a transurethral resection of bladder tumor and insertion of ureteric stents.

Histopathological examination showed scant material composed of epithelium only and was insufficient for a conclusive diagnosis. A second transurethral resection of bladder tumor performed 4 weeks later showed non-specific active chronic inflammation. Clinical suspicion persisted and a third transurethral resection of bladder tumor was performed 6 weeks later. A portion of the biopsy was sent for flow cytometry but there were insufficient lymphoid cells for analysis. Histology showed urothelium infiltrated by mixed inflammatory cells. Centered within the muscularis propria, sheets of malignant cells were noted. The malignant cells were composed of predominantly atypical intermediate size cells admixed with some larger cells. There were high grade features, characterized by apoptosis and frequent mitotic figures. The larger cells showed multi-nucleation and variable prominent nucleoli, some of which showed wreath-like nuclear arrangement (Figure 1A and 1B).

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Figure 1.

(A) H&E – × 100 magnification showing infiltration of muscularis propria by diffuse sheets of malignant cells; (B) × 200 magnification showing a large multinucleated cell with wreath-like arrangement.

Based on morphology, the differential diagnoses were broad and included poorly differentiated carcinoma, high grade lymphoma and metastatic melanoma. The lack of an in situ component and tumor centered within the muscularis propria were against a primary urothelial carcinoma. The presence of characteristic wreath-like nuclei was suspicious for ALCL.

By immunohistochemistry, the cells were diffusely positive for CD45, CD43, BCL2 and CD30. There was weak patchy positivity for CD2, CD3 and CD5; whereas CD4 and CD8 showed strong patchy positivity. MUM1 was positive in 70% of cells. The malignant cells were positive for p63 (80% of cells) and GATA3 showed patchy nuclear staining. There was no staining with keratin AE1/3, keratin CAM5.2, EMA, p40, keratin 5, uroplakin 2, CD20, PAX5, CD10, CD21, ALK, CD138, TDT(DNTT), perforin, TIA1, granzyme B, myeloperoxidase and Epstein-Barr encoding region in situ hybridization (EBER-ISH) (Figure 2A to 2E). The morphological features and immunophenotype were diagnostic of a T cell lymphoproliferative malignancy and ALK-negative ALCL was favored due to the diffuse CD30 positivity.

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Figure 2.

(A) Immunohistochemistry staining at 200 ×  magnification with CD30 demonstrating diffuse strong cytoplasmic positivity; (B) p63 shows diffuse nuclear staining; (C) CD3 is patchy positive staining lesional cells including large cells; (D) negative staining for p40; (E) negative staining for uroplakin 2; (F) FISH studies with a dual-colour break-apart probe showing TP63 disruption – demonstrated by the separation of the red/green signal within the white circle.

Further ancillary testing was performed. T-cell receptor (TCR) gene rearrangement studies showed reproducible monoclonal TRB and TRG arrangements. Fluorescence in-situ hybridization (FISH) studies analyzing break-apart for DUSP22/IRF4 and TP63 were performed. TP63 rearrangement was detected (Figure 2F) but there was no DUSP22/IRF4 rearrangement.

The patient was referred to Haematology for further management. Further investigation including imaging with positron emission tomography showed no evidence of disease elsewhere in the body (disease stage IE), and he was commenced on CHOP-21 chemotherapy for 6 weeks. Follow up imaging studies 7 months post diagnosis showed leptomeningeal metastasis, and 3 months later he presented to the emergency department with severe neurological symptoms. The patient was treated palliatively and died the following week.

Discussion

According to the current World Health Organization classification of systemic ALCL is subdivided into ALK-positive and ALK-negative subtypes. Both subtypes share similar morphology and are differentiated only on ALK positivity. ALK-positive is more frequent in children and young adults, whereas ALK-negative occurs in older individuals. Both subtypes show male predominance (M:F 1.5:1).^6–8

Regardless of the subtype, it is composed of a spectrum of small and large neoplastic cells that demonstrate universal expression of CD30 antigen. ⁹ The most commonly described large cells are the hallmark cells, which contain eccentric horseshoe/kidney-shaped nuclei and a prominent paranuclear eosinophilic Golgi.

As aforementioned, our case showed positive staining for p63 and GATA3. Expression of these two markers is well known in ALCL and can be difficult to distinguish from urothelial carcinoma which expresses both of these markers. In addition, studies have shown that ALCL cases can be negative for CD3 and CD45. ALCL can also show a null T cell phenotype and this is when positive cytotoxic markers can be useful. An accurate diagnosis is crucial as the management is significantly different. To avoid misdiagnosis a comprehensive immunohistochemistry panel is necessary. This is of particular importance in poorly differentiated carcinomas or atypical lymphoproliferative proliferations and in samples with limited material. Additional immunohistochemical stains such as multiple cytokeratins, uroplakin 2, and p40 are also helpful to exclude urothelial carcinoma.

On a molecular level, small case series have detected two common rearrangements that have prognostic implications; [1] DUSP22 rearrangements are identified in about 30% of cases; and [2] TP63 rearrangements occurs in about 8% of cases.^10–12 DUSP22 rearrangement confers good prognosis whereas TP63 rearrangement is associated with poor prognosis. TP63 cases have a significantly worse 5 year overall survival rate when compared with cases without any rearrangements (17% vs. 42%). ¹⁰ Our case had TP63 disruption and the patient did succumb to the disease ten months after his diagnosis. It is also worth noting that p63 positivity by immunohistochemistry is not specific for TP63 disruption; hence, this needs to be investigated via FISH studies, but p63 immunohistochemistry can be useful as a screening test. ¹³

In summary, we report a novel case of ALK-negative ALCL primary to the urinary bladder with emphasis on potential pitfalls in misdiagnosis due to the overlap of histological and immunohistochemical features with urothelial carcinoma and provide information on recent molecular findings reported in the literature.