Explore bladder cancer and urothelial neoplasms: types, epidemiology, and key risk factors like smoking. Understand its pathogenesis & progression from non-inva
DISORDERS OF THE LOWER URINARY TRACT — PART 2 --- 3. NEOPLASMS OF THE URINARY BLADDER Overview: - Bladder cancer = 9th most common cancer worldwide - 95% of bladder tumours are of epithelial origin - Urothelial neoplasms = by far the most common type, followed by squamous and glandular neoplasms Classification of Bladder Tumours: - Urothelial (transitional) tumours — noninvasive and infiltrating - Squamous cell carcinoma - Adenocarcinoma - Mixed carcinoma - Small-cell carcinoma - Sarcomas --- A. UROTHELIAL NEOPLASMS Overview: - Represent ~ 90% of all bladder tumours - Range from small benign lesions that never recur → aggressive fatal cancers - Many are multifocal at presentation - Can arise anywhere urothelium exists — from renal pelvis to distal urethra Two Distinct Precursor Lesions to Invasive Urothelial Carcinoma: - Noninvasive papillary tumours — originate from papillary urothelial hyperplasia; most common precursor - Flat noninvasive urothelial carcinoma in situ (CIS) — cytologically malignant cells confined to epithelium; no basement membrane invasion; always considered high grade ⚠️ In ~50% of invasive bladder cancer cases, the tumour has already invaded the bladder wall at presentation — precursor lesion destroyed by the high-grade invasive component. Prognostic Key: - Invasion into lamina propria → worsens prognosis - Invasion of muscularis propria (detrusor) → major survival drop → 30% 5-year mortality --- Epidemiology: - Male-to-female ratio = 3:1 - Higher incidence in high-income nations and urban dwellers - ~80% of patients aged 50–80 years - Rarely familial Risk Factors: - Cigarette smoking — increases risk 3–7× depending on duration and type of tobacco use; single most important risk factor - Industrial aryl amine exposure — particularly 2-naphthylamine ; cancer appears 15–40 years after first exposure - Schistosoma haematobium — 70% of associated cancers are squamous; remainder urothelial or glandular - Long-term analgesic use - Heavy/long-term cyclophosphamide exposure - Irradiation --- Pathogenesis — Two Molecular Pathways: Pathway 1 — Non-muscle-invasive papillary cancers: - Gain-of-function alterations → ↑ signalling through growth factor receptor pathways - Common mutations: FGFR3 tyrosine kinase receptor gene amplifications + activating mutations in RAS and PI3-kinase - These tumours frequently recur but progress to muscle-invasive cancer in only ~ 20% of cases Pathway 2 — Muscle-invasive cancers (via flat CIS): - Majority develop by progression from flat CIS - p53 and RB mutations prevalent in all muscle-invasive cancers - p53/RB mutations occur early in CIS development but later in papillary cancer progression - High somatic mutation burden — comparable to lung cancer and melanoma (underscoring carcinogen exposure role) --- Morphology: - Papillary lesions: red, elevated excrescences; <1 cm up to 5 cm; often multiple discrete tumours Papilloma (Exophytic): - Represents ≤ 1% of bladder tumours; seen in younger patients - Small (0.5–2 cm); delicate; attached to mucosa by a stalk - Finger-like papillae with central fibrovascular core covered by histologically normal urothelium - Recurrences and progression rare but possible Inverted Papilloma: - Completely benign - Inter-anastomosing cords of cytologically bland urothelium extending into the lamina propria - ⚠️ Simulates an invasive process histologically — do not confuse Papillary Urothelial Neoplasm of Low Malignant Potential (PUNLMP): - Similar to papilloma but with thicker urothelium and greater cell density - Larger than papillomas on cystoscopy; may be indistinguishable from papillary cancers - Recurrent tumours usually show same morphology - Progression to higher grade: rare Low-Grade Papillary Urothelial Carcinoma: - Orderly architecture; low-grade cytologic atypia - Cells evenly spaced (maintain polarity) and cohesive - Scattered hyperchromatic nuclei; infrequent mitoses (predominantly basal); slight nuclear size/shape variation - May recur and infrequently invade - Rarely life-threatening High-Grade Papillary Urothelial Carcinoma: - Dyscohesive cells with large hyperchromatic nuclei, irregular chromatin, prominent nucleoli - Some cells highly anaplastic - Frequent mitoses including atypical mitoses - Architectural disarray + loss of polarity - Much higher rate of progression to muscle-invasive cancer - Significant potential for metastasis → regional lymph nodes, liver, lung Carcinoma In Situ (CIS) / Flat Urothelial Carcinoma: - Cytologically malignant cells within a flat urothelium — no invasion - Ranges from full-thickness cytologic atypia → scattered malignant cells in otherwise normal urothelium ( pagetoid spread ) - Shared feature with high-grade papillary carcinoma: lack of cohesiveness → malignant cells shed into urine - Extensive shedding → few CIS cells left clinging to a denuded basement membrane - Cystoscopy: mucosal reddening, granularity, or thickening — no intraluminal mass - Commonly multifocal ; may involve most of bladder + extend into ureters and urethra - ⚠️ If untreated: 50–75% progress to invasive cancer Invasive Urothelial Carcinoma: - May be associated with high-grade papillary cancer or adjacent CIS - Stage = most important prognostic factor — based on depth of invasion in bladder wall - Muscularis propria invasion → indication for radical cystectomy or radiation therapy ± neoadjuvant/adjuvant chemotherapy - Unusual variants: nested (deceptively bland cytology), lymphoepithelioma-like, micropapillary, sarcomatoid carcinoma Clinical Features of Urothelial Carcinoma: - Painless haematuria = most common presenting symptom - May also have: frequency, urgency, dysuria - Ureteral orifice obstruction → pyelonephritis or hydronephrosis - Prognosis depends on grade and stage — key variable = muscle-invasive vs. non-muscle-invasive --- B. OTHER EPITHELIAL BLADDER TUMOURS Squamous Cell Carcinoma: - Common in areas where urinary schistosomiasis is endemic - Arises from atypical keratinizing mucosa (squamous dysplasia and CIS) - Nearly always associated with chronic bladder irritation and infection - ⚠️ Mixed urothelial carcinoma with squamous areas is more common than pure squamous cell carcinoma Adenocarcinoma: - Rare; histologically identical to GI tract adenocarcinomas - Some arise from urachal remnants or in association with extensive intestinal metaplasia Small-Cell Carcinoma: - Indistinguishable from small-cell carcinoma of the lung - Often occurs in association with urothelial, squamous, or adenocarcinoma - Very aggressive - Strongly associated with loss-of-function mutations in TP53 and RB tumour suppressor genes --- C. MESENCHYMAL TUMOURS Benign: - Great variety; collectively rare - Most common = leiomyoma - Grow as isolated, intramural (submucosal), encapsulated, oval-to-spherical masses — up to several centimetres Sarcomas: - True sarcomas uncommon in the bladder - ⚠️ Inflammatory myofibroblastic tumours and sarcomatoid carcinomas are more common than true sarcomas - Tend to produce large masses (up to 15 cm) protruding into the vesicle lumen; soft, fleshy, grey-white - Infants/children → most common bladder sarcoma = embryonal rhabdomyosarcoma ; may manifest as a polypoid grape-like mass = sarcoma botryoides - Adults → most common bladder sarcoma = leiomyosarcoma --- D. SECONDARY TUMOURS - Most common = direct extension from adjacent organ cancers: cervix, uterus, prostate, rectum - Lymphoma may involve bladder as part of systemic disease - Metastatic spread of solid tumours to bladder: very rare --- 4. OBSTRUCTION Overview: - Bladder outlet obstruction is clinically important because of its eventual effect on the kidneys - Males: most common cause = benign prostatic hyperplasia (BPH) - Females: most often caused by cystocele Other Causes: - Congenital or inflammatory urethral strictures - Inflammatory fibrosis and contraction of the bladder - Bladder tumours - Invasion of bladder neck by tumours from contiguous organs - Foreign bodies and calc