- pTX: cannot be assessed
- pT0: no evidence of primary tumor
- pTa: noninvasive papillary carcinoma
- pTis: carcinoma in situ
- pT1: invades lamina propria
- pT2a: invades inner half of muscularis propria
- pT2b: invades outer half of muscularis propria
- pT3a: microscopically invades perivesical tissue
- pT3b: macroscopically invades perivesical tissue
- pT4a: directly invades prostatic stroma, seminal vesicles, uterus or vagina
- pT4b: directly invades pelvic wall or abdominal wall
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Lamina propria (pT1)
- Lamina propria contains connective tissues between urothelium and detrusor muscle (muscularis propria), made of loose stroma, variably sized blood vessels and thin muscle bands of muscularis mucosae (see Histology)
- Has nests, clusters or single tumor cells, sometimes with prominent retraction artifact (mimics lymphovascular invasion)
- Often has desmoplastic or inflammatory stromal response and absent or irregular basement membrane (not seen with noninvasive low grade papillary carcinoma with inverted pattern)
- Tumor cells often have abundant eosinophilic cytoplasm at advancing edge (paradoxical differentiation) but have enlarged, malignant appearing nuclei
- If tumor cells hug the mucosa, they should be more anaplastic than benign mucosal cells
- Pitfalls include tangential sectioning, poor specimen orientation, inflammation, thermal injury, deceptively bland cytology and pseudoinvasive nests of nonneoplastic proliferative urothelial cells (Pathology 2003;35:484)
- Subcategorization of pT1 based on muscularis mucosae is difficult and may not correlate with progression (Mod Pathol 1996;9:1035, Arch Pathol Lab Med 2022;146:1131)
- Other strategies for the subcategorization of pT1 (such as based on depth of invasion) have been proposed but are not a part of AJCC staging (Arch Pathol Lab Med 2022;146:1131)
- pTa cases may actually be invasive when studied by electron microscopy; significance is unclear (Am J Clin Pathol 2003;120:188)
- Invasion of lamina propria (pT1) is not as clinically crucial as invasion of muscularis propria (pT2)
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Muscularis propria (pT2)
- Muscularis propria is thick aggregated muscle bundles of detrusor muscle; must distinguish from hypertrophic muscularis mucosae (Am J Surg Pathol 2007;31:1420)
- Muscularis propria presence should be specified in transurethral resections and cold cup biopsies
- Muscularis propria invasion prompts definitive therapy, typically cystectomy with or without neoadjuvant therapy
- Can use muscle markers such as desmin or SMA to highlight muscle and keratins such as AE1 / AE3 to highlight carcinoma in challenging cases
- Difficult to subcategorize as pT2a or pT2b unless the pathologist has full thickness bladder wall and well oriented section such as in a cystectomy specimen and thus would not be documented in biopsy or transurethral resection of bladder tumor (TURBT) specimens
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Perivesical fat (pT3)
- Perivesicular adipose tissue is deep to muscularis propria but is also present within deep lamina propria, usually as small localized aggregates and within muscularis propria (superficial and deep)
- Beware of inappropriate classification as pT3 due to tumor infiltration of adipose within the lamina propria, particularly in TURBT specimens (Am J Surg Pathol 2000;24:1286)
- Note that the gross prospector must document the impression of perivesicular adipose invasion to allow for subcategorization as pT3a versus pT3b as pT3b requires macroscopic invasion
- Many cases lack the gross impression of perivesicular adipose invasion and thus cannot be accurately classified (Hum Pathol 2017;61:190)
- Subcategorization into pT3a and pT3b has an uncertain prognostic impact with some studies showing no difference in outcome (Virchows Arch 2012;461:467)
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Prostate gland (pT4 versus pT2)
- If carcinoma of the bladder transmurally invades through the bladder wall and into the prostatic stroma, the tumor is designated as pT4a
- If carcinoma of the bladder colonizes the prostatic urethra via in situ spread and then invades the underlying prostatic stroma, it is not pT4a (but can be considered a separate tumor of the prostatic urethra with a pT2 designation; see Staging of the prostatic urethra)
- Survival of patient with pT4 tumors is poor (median: < 1 year; 1.5 year survival: < 15%) (Virchows Arch 2012;461:467)