Selected Urothelial Lesions of Urinary Bladder and Their Common Diagnostic Pitfalls

Cheng Wang, FRCPC, FCAPDepartment of Pathology and Laboratory Medicine

QEII health center and Dalhousie UniversityApril, 2015

Disclosure

• Conflict of interest– None

Objectives

• Be able to identify the histopathological features and grasp the diagnostic criteria for the selected urothelial lesions

• Be able to generate important differential diagnoses based on their histomorphological characteristics and develop practical approach to further work-up

Urinary bladder cancer

• Seventh most common cancer worldwide• In North American, over 90% of urothelial

origin

Bladder Cancer – Etiology• Risk factors

Age Urothelial carcinoma is rare in young people

Gender Approximately 3 times more common in men than women

Smoking Cigarette smoking most important factor related to bladder cancer more than 50% in men and more than 35% in women due to cigarette smoking

Occupational exposure: paint, rubber, leather industries (exposure to organic chemicals)

Aniline dye Aromatic amines

Medication: Analgesics such as phenacetin Cyclophosphmide Cholrnaphazine

Infections Schistosoma hematobium

Pathology of the Urinary Tract Neoplasms

Superficial (Noninvasive) growth (70%)-Papillary - exophytic

-Flat - intraepithelial (Carcinoma in-situ)

Invasive growth (30%)-Starts as invasive carcinoma

-Progression from superficial to deep

Flat Urothelial Lesions ranging from urothelial hyperplasia, reactive atypia,

dysplasia and urothelial CIS

Urothelial carcinoma in situ (CIS)• High-grade urothelial carcinoma confined to the urothelium that is confined within

basement membrane of urothelium.

Epidemiology• Similar distribution to invasive urothelial carcinomas• Risk factors: tobacco smoke and exposure to industrial compounds such as aromatic amines• Common in the sixth to seventh decades, can be as young as 30 years• Males gender

Presentation • Generally identified in association with invasive urothelial carcinoma • Hematuria, dysuria, or urgency • Cystoscopically, urothelium oftenappears erythematous

Urothelial Carcinoma in Situ (CIS) Three clinical forms:

Primary (de novo) CIS: Isolated CIS without prior or concurrent papillary neoplasm (rare).

Secondary CIS: In patients with prior papillary neoplasm.

Concurrent CIS: Identified on bladder mucosa with concomitant papillary neoplasm or invasive carcinoma.

Prognosis• ~ 50% of patients develop invasive carcinoma within 5 years

Diagnostic Criteria for Urothelial CIS (mainly a cytological diagnosis)

1. Enlarged, pleomorphic and hyperchromatic nuclei

2. Coarse or condensed chromatin3. Complete loss of polarity, marked crowding4. Mitoses are common and can extend into the

upper cell layers5. Any malignant cells are sufficient for CIS,

ranging from isolated cells (pagetoid) to full-thickness atypia

Urothelial CIS, just scattered atypical cells, instead of full thickness involvement

Frozen section of ureter margins in radical cystectomy specimen

• Ureteric mucosal margin evaluation• Generally En face section including entire wall (urothelium,

muscularis, and adventitia)• Frozen section artifact may cause “atypical” features, so

first identify normal urothelium (with longitudinal nuclear grooves and normal polarity)and use it as an internal “built in” control

• Be aware of urothelial Ca variants such as plasmacytoid pattern within the adventitia, which resembles inflammatory cells

• von Brunn nests are common and should be distinguished from invasive Ca

Nuclear size enlargement threshold : 4x-6x of a mature lymphocyte nucleus

[998] Poropatich et. al. Nuclear Size Measurement for Distinguishing Urothelial Carcinoma From Reactive Urothelium on Tissue Sections

Conclusion: High grade urothelial carcinoma including CIS had much greater nuclear enlargement than reactive urothelium.

Design: We measured the nuclear size (length and width) of individual urothelial cells on digital images from H&E tissue sections, using standard imaging CellSens software. At least 10 urothelial cells were measured in each image. Lymphocytes on the corresponding sections were also measured as the standard. The specimens studied include reactive urothelium (RU; n=5), low grade UC (n=12) and high grade UC (n=7) including carcinoma in situ (CIS, n=4).

Results: The length (L) and width (W) of 289 cells are measured on bladder H&E sections. The area was calculated by WxLx0.8 based on the oval shape of most urothelial cells. Lymphocyte (LC) area and diameter were determined. These data are in the table below:

Pitfalls for Urothelial CIS

Case 1: Radiation cystitis

• Urothelium exhibits marked cytologic atypia characterized by nuclear pleomorphism, smudgy chromatin and cytoplasmic vacuolations, but with normal or maintained N/C ratio

• Background stroma also exhibits pronounced atypia

• Blood vessels are thickened and hyalinized

• Lamina propria with edema or fibrosis

• Pseudocarcinomatous epithelial hyperplasia may develop which can closely mimic carcinoma.

Case 2: Polyoma Virus Infection• Characterized by large, homogeneous basophilic nuclear

inclusions (“decoy cells”)• Enlarged cell with round nucleus, smooth border, ground

glass with marginated chromatin• Maybe some overlap with high grade cells• Some reports on the co-existence of Decoy cells and high

grade UC/CIS in urine cytology• Some reports indicate the Polyoma virus is likely causing

bladder Ca in kidney transplant patient. Careful follow-up of immunocompromised patient is recommended.

• SV40 immunostain to confirm Polyoma virus infection

Urothelial Carcinoma in Situ can involve Von Brunn’s Nests or cystitis cystica, which need to be

differentiated from Endometriosis

Case 4: Radical Prostatectomy, 70M what is the intraductal lesion with high grade

nuclear atypia and necrosis?

Case 5: Core needle biopsy of Prostate, 60 M, shows intraductal component with high grade nuclear atypia and comedonecrosis

Urothelial CIS involving prostatic ducts Vs. Intraductal adenocaricnoma of prostate (IDCP)

• IDCP criteria– solid intraductal growth

– dense cribriform

– loose cribriform/micropapillary with nuclear size >6x normal

– Comedonecrosis

– dilated ducts >2x normal

• Intraductal Urothelial CISo Marked nucleomegaly (4-

6x size of a normal lymphocyte nucleus)

o Coarse, condensed nuclear chromatin

o Mitoses including atypical forms

o Loss of polarity and crowding

Guidelines for IHC in differentiating UC Vs. High grade Pca

UC versus Pca

• First line markers:– PSA and GATA3

• Second line markers:– HMWK, p63, PAP,

P501S and NKX3.1

Case 6: Urothelial Papilloma• Clinical Issues

– Very uncommon urothelial lesion (~ 1% of papillary urothelial neoplasms)– Typically occur in younger adults and are seen in children– Gross or microscopic hematuria– Recurrence is rare (0-8%)– Posterior or lateral walls of bladder, close to ureteral orifices– Urethra is another common site of occurrence

• Microscopic Pathology– Exophytic papillary neoplasm lined by urothelium in normal thickness– No significant cytologic atypia, mitosis rare to absent.– Slender, minimally branching papillary architecture

• Main Differential Diagnosis:– Nephrogenic adenoma/hyperplasia– Polypoid/papillary cystitis– Fibroepithelial polyp of the urathra– Prostatic type polyp of the urathra– Ductal adenocarcioma of prostate

Case 7: Bladder papillary lesion: nephrogenic adenoma/hyperplasia

Case 7: Nephrogenic adenoma/Hyperplasia• Etiology/Pathogenesis

– Many are secondary to urothelial injury

• Clinical Issues– Usually incidental microscopic findings– May have irritative symptoms from underlying inflammatory process

• Macroscopic Features– May appear as papillary-polypoid mass or irregular flat velvety lesion

• Microscopic Pathology– Papillary cores lined by single cuboidal epithelial layer– Tubular pattern with "hobnail" arrangement of epithelial cells– Rare cases have myxoid stroma and cording or spindling of cells (fibromyxoid pattern)– Rare cases have diffuse sheet-like growth– Thick basement membrane/hyalinized sheath may underlie epithelium– Degenerative-type atypia may be present

• Ancillary Tests– Express cytokeratins and pax-8– May express PSA, PAP, and AMACR

Case 8: Polypoid/papillary Cystitis• Terminology

– Papillary cystitis is nonneoplastic inflammatory lesion of urinary bladder, Characterized by edema of lamina propria and exophytic polypoid or papillary projections

• Etiology/Pathogenesis– Many cases are related to indwelling catheter or vesical fistula

• Clinical Issues– May affect any age group– Hematuria– Irritative bladder symptoms from underlying cause– No excision required

• Microscopic Pathology– Characterized by variable exophytic projections of urothelium secondary to lamina propria edema– Papillae lack complex branching typical of papillary urothelial neoplasia– Stromal cores are comprised of edema and fibrosis, not typical fibrovascular cores of papillary

urothelial neoplasia– Stromal cores are characteristically broader at base and taper to point distally– Reactive urothelial atypia may be prominent

Case 9: Male patient, papillary Lesion from prostatic urethra

PSA positive in the papillary lesion, Differential diagnosis?

DDx 1: Prostatic type Polyp• Etiology/Pathogenesis

– Multiple theories proposed

• Clinical Issues– Broad range: 19-89 years– Trigone is most common site in bladder– Most common in prostatic urethra– Hematuria, hematospermia– Polypoid mass with variable exophytic fronds

• Microscopic Pathology– Polypoid or papillary/filiform exophytic process– Stroma contains benign prostatic-type secretory glandular epithelium and admixed

urothelium– Excrescences lined by cytologically benign prostatic secretory cells &/or urothelium– Long, finger-like projections are rarely seen

Higher power of the current urethral papillary lesion showing columnar cells with enlarged nuclei, prominent nucleoli and

amphophilic cytoplasm

Case 9 Final Dx: Ductal prostatic adenocarcinoma 8/10 (4,4)

• Terminology– Adenocarcinoma of prostatic epithelial cell origin with large glandular and papillary architecture lined by

tall columnar cells, often with pseudostratified growth

• Clinical Issues– Pure ductal adenocarcinoma accounts for 0.4-0.8% of all prostate cancers– Mixed ductal and acinar adenocarcinoma reported in 5-6.3% of prostate cancers– Most studies suggest a more aggressive clinical behavior than acinar adenocarcinoma

• Macroscopic Features– Centrally located tumors can have exophytic friable fronds protruding in urethral lumen– Peripheral tumors are more often posteriorly situated as firm, gray-white parenchymal mass

• Microscopic Pathology– Main architectural patterns: Papillary, cribriform, individual glands, solid– Tall columnar cells in single or pseudostratified growth pattern– Cytoplasm usually amphophilic and nucleus oblongated with variably prominent nucleolus– Can grow intraluminally into preexisting ducts retaining "native" basal cell layer– Positive for AMACR in 77% of cases– Majority has no detectable basal cells by p63 or HMCK(34βE12)– ISUP 2005 consensus recommends grading as Gleason pattern 4; if necrosis is present, pattern 5

High Grade Papillary Urothelial Carcinoma (can be a spectrum)

Higher than low grade and, yet, lower than high grade? Grade 2.5?

• High grade but low end of the spectrum• What are the features might be helpful to

determine if high grade or not?1. Nuclear atypia (enlargement and coarse chromatin)2. Mitosis and apoptotic bodies3. Papillary fusion/necrosis4. Invasive components (but low grade papillary

urothelial carcinoma can rarely be invasive)

High-grade papillary urothelialcarcinoma with lamina propria invasion

• Features favor stromal invasion– Histologic grade: usually high nuclear grade– Irregularly shaped nests– Single cell infiltration– Paradoxical differentiation– Stromal inflammatory response– Desmoplasia or fibrotic stroma– Retraction artifact– Myxoid stroma

Lymphovascular invasion versus retraction artifact

• Vascular invasion may be present, which must be distinguished from retraction artifact, by– the presence of endothelial cell lining – associated red blood cells– muscle wall

Invasion versus Inverted/endophytic growth

• Inverted urothelial lesion is beneath the surface urothelium and shows a smooth, non-destructive outlines.

Variants of Urothelial Ca

• Be aware of the bland cytology of nested and microcystic variants, which can be challenges to diagnose in a small sample.

Clear Cell Variant of Invasive Urothelial Carcinoma

DDx: Metastatic clear cell RCC, Spreading of Clear cell adenocarcinoma of Mullerian origin and Metastatic prostate AdenoCa

Case 10: Suptum ctyology from a 61F, history of DVT for two months, now severe SOB. Imaging shows liver, bone, chest hilar

lesions and a bladder mass

• Sputum cytology showing 3D-clusters of atypical cells with enlarged nuclei and cytoplasmic vacuoles

Autopsy Findings• Patient passed away three days after

presenting to hospital. The bladder tumor is invasive urothelial carcinoma containing both micropapillary and plasmacytoid variants

• Distant metastasis in Bone, heart, liver, lymph nodes and brain were identified

Lung Metastatic Micropapillary Variant of Invasive Urothelial Carcinoma, the

morphology of which resembles to the atypical cells seen in sputum cytology

Urothelial Carcinoma Micropapillary Variant

• More frequent in elderly men (M:F 5:1, mean age: 66) and present with hematuria

• Often co-exists with the conventional urothelial carcinoma. Pure micropapillary variant is rare (about 1% of all urothelial carcinoma).

• Most cases of the micropapillary variant are high stage cancer at diagnosis with frequent lymph node metastasis

• Need to report MP variant (using specific morphology criteria) in the invasive component

• Be aware of retraction artifact can be mistaken as MP variant

MP variant tends to metastasize to lymph nodes

Important to recognize the cytological features of potential micropapillary variant in Urine Cytology specimens, especially

those not accompanied by tissue bx

Small cell carinoma of urinary bladder

• Sheets and occasionally nests of cells with scant cytoplasm and high n/c ratio

• Chromatin is finely stippled, and nucleoli are inconspicuous• Geographic areas of necrosis, high mitotic rate, and areas of crush artifact

are also frequent• Other subtypes of primary bladder carcinoma may be admixed

– Urothelial carcinoma in situ, invasive urothelial carcinoma, squamous cell carcinoma, adenocarcinoma, or sarcomatoid carcinoma

• Highly aggressive clinical behavior• Even focal small cell component should be reported

Reference

• Ming Zhou, Genitourinary Pathology, Expert Consult series

• Amin et al. Diagnostic Pathology: Genitourinary• Cheng et al., Bladder Pathology• Cibas and Ductaman: Cytology Diagnostic

Principles and Clinical Correlates