A. Benign Tumors

1. Hyperplastic
   1. Brunn's epithelial nests
   2. Cystic cystica
   3. Cystitis follicularis
   4. Cystitis glandularis
   5. Often follow recurrent urinary tract infections (mainly in women)
   6. Usually found in bladder trigone
2. Metaplastic and Tumor-Like Lesions
   1. Inverted papilloma - usually in bladder trigone or neck
   2. Nephrogenic adenoma - usually associated with previous surgery or bladder trauma
   3. Eosinophilic granuloma

B. Malignant Tumors

1. Malignant Primary Neoplasms
   1. Transitional cell carcinoma (85% of malignant tumors)
   2. Squamous cell carcinoma
   3. Adenocarcinoma
   4. Mixed carcinoma
   5. Sarcoma (leiomyoscarcoma)
2. Metastatic Cancers
   1. Renal
   2. Gastric
   3. Melanoma
   4. Lymphoma
3. Local Invasion
   1. Vaginal cancer
   2. Colorectal
   3. Cervical

C. Inflammatory Lesions

1. Infection
   1. Schistosoma haematobium
   2. Fungal
   3. Viral
   4. Condyloma acuminatum
2. Non-Infectious
   1. Malacoplakia - granulomatous lesion, may be related to E. coli infection
   2. Malacoplakia may be due to defective phagocytosis by histiocytes
3. Inflammatory Pseudotumor
   1. Mainly in women in their 30s
   2. Inflammation may be partial or full thickness in bladder wall
   3. Mass composed of spindle cells in vascular myxoid matrix
   4. Treatable by complete excision of the lesion
4. Atypical Cystitis
   1. Polypoid cystitis associated with catheter or fistula
   2. Cystitis glandularis
   3. Radiation cystitis

D. Other

1. Endometriosis of bladder
2. Amyloidosis
3. Post-operative spindle cell nodule

References

1. Blute RD Jr and Oliva E. 2000. NEJM. 343(15):1105
2. Heney NM and Young RH. 2003. NEJM. 349(25):2442 (Case Record)