Table 2.
The 2016 PSOGI, 2017 AJCC, and 2019 WHO pathological classification and terminology of the PMP
| 2016 PSOGI classification | Counterparts | |
|---|---|---|
| 2017 AJCC staging system, 8th edition (TNM) | 2019 WHO classification of tumors, 5th edition | |
|
AM: (1) Mucin without neoplastic epithelium; (2) Confined to or distant from organ surface |
M1a | pM1a |
|
LMCP: (1) Low-grade cytology; (2) Rare mitosis; (3) Few tumoral mucinous epithelium (< 20% of tumor volume) |
M1b. G1, well-differentiated |
pM1b, Grade 1: (1) Hypocellular mucinous deposits; (2) Neoplastic epithelial elements have low-grade cytology; (3) No infiltrative-type invasion |
|
HMCP: Features of one or more of the following (At least focally): (1) high-grade cytology; (2) Infiltration of adjacent tissues; (3) Invasion of vascular lymphatic vessels or surrounding nerves; (4) Cribriform growth; (5) Neoplastic mucinous epithelium (> 20% of tumor volume); Sub-classification based on differentiation (1) well-differentiated: Mainly composed of single- tubular glands; Tumor cell polarity exists; Obvious tumor cell atypia; Infiltrative components; (2) Moderately-differentiated: Solid sheet tumor cells mixed with adenoid structures; Minimal or no polarity; (3) Poorly-differentiated: Highly irregular to no adenoid differentiation Cell polarity disappears |
M1b. G2 or G3, moderately- or poorly-differentiated |
pM1b, Grade 2: (1) Hypercellular mucinous deposits as judged at 20 × magnification; (2) High-grade cytological features; (3) Infiltrative-type invasion characterized by jagged or angulated glands in a desmoplastic stroma, or a small mucin pool pattern with numerous mucin pools containing clusters of tumor cells |
|
HMCP-S: Tumor with signet ring cell component (signet ring cells ≥ 10%) |
M1b. G3, poorly- differentiated; PMCA-S |
pM1b, Mucinous tumor deposits with signet-ring cells |
PMP, pseudomyxoma peritonei; PSOGI, Peritoneal Surface Oncology Group International; AJCC, American Joint Committee on Cancer. AM, acellular mucin; LMCP, low-grade mucinous carcinoma peritonei; HMCP, high-grade mucinous carcinoma peritonei; HMCP-S, high-grade mucinous carcinoma peritonei with signet ring cells; DPAM, disseminated peritoneal adenomucinosis; PMCA-I, peritoneal mucinous carcinomatosis with intermediate feature; PMCA, peritoneal mucinous carcinomatosis; NA, not applicable