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Table 1 The PNM classification of alveolar echinococcosis

From: Primary extrahepatic alveolar echinococcosis of the lumbar spine and the psoas muscle

P

Hepatic localization of the parasite

PX

Primary tumor cannot be assessed

P0

No detectable tumor in the liver

P1

Peripheral lesions without proximal vascular and/or biliary involvement

P2

Central lesions with proximal vascular and/or biliary involvement of one lobe (a)

P3

Central lesions with hilar vascular or biliary involvement of both lobes and/or with involvement of two hepatic veins

P4

Any liver lesion with extension along the vessels (b) and the biliary tree

N

Extra-hepatic involvement of neighboring organs [diaphragm, lung, pleura, pericardium, heart, gastric and duodenal wall, adrenal glands, peritoneum, retroperitoneum, parietal wall (muscles, skin, bone), pancreas, regional lymph nodes, liver ligaments, kidney]

NX

Not evaluable

N0

No regional involvement

N1

Regional involvement of contiguous organs or tissues

M

The absence or presence of distant Metastasis [lung, distant lymph nodes, spleen, CNS, orbita, bone, skin, muscle, kidney, distant peritoneum and retroperitoneum]

MX

Not completely evaluated

M0

No metastasis (c)

M1

Metastasis

  1. (a) For classification, the plane projecting between the bed of the gall bladder and the inferior vena cava divides the liver in two lobes
  2. (b) Vessels mean inferior vena cava, portal vein and arteries
  3. (c) Chest X-ray and cerebral CT negative