Metastases

A brain metastasis. H&E stain.

Metastases are tumours that have spread from elsewhere and are separate from the initial (primary) lesion; usually, they are an ominous finding. They may also be referred to as secondary tumours.

Seen from pathology, metastatic disease and direct extension of a tumour (on a biopsy) may be distinguishable.

Metastases are not always obvious when encountered; thus, metastasis should be considered with every diagnosis of a malignant tumour.

Cancers of unknown primary are dealt with in the cancer article. A general approach to undifferentiated tumours is given in the basics article under the heading modified general morphologic DDx of malignancy.

Lymph node metastases are dealt with in the article lymph node metastases.

A handful of things have metastatic-like behaviour but are not malignant. Examples of benign things with metastatic-like behaviour are: benign metastasizing leiomyoma, endometriosis, endosalpingiosis and benign nevus cells (in lymph nodes).

Special types

In-transit metastasis

Definition - the separate tumour nodule must be:

1. >2 cm from the primary tumour.
2. Arises between the nearest (regional) lymph nodes and the primary tumour.
   • The tumour presumably arises from a lymphatic that drains the tissue in which the primary tumour grew.

Notes:

• It is called "in-tranist", as it happens while the tumour is on the way to the regional lymph node.
• In-transit metastases are seen in malignant melanoma, merkel cell carcinoma.
• If a separate tumour nodule <= 2 cm from the primary tumour, it is known as satellitosis.

Specific sites

Internal organs

Main article: Liver metastasis

Main article: Lung metastasis

Main article: Kidney metastasis

Lymph node

Main article: Lymph node metastasis

Other

Main article: Peritoneal metastasis

Main article: Testicular metastasis

Brain

Main article: Brain metastasis

Specific tumours

Melanoma

Main article: Metastatic melanoma

Osteosarcoma

Main article: Osteosarcoma

• Giant cells.

IHC

• Dependent on (suspected) primary.

Not necessary to do stains/immunostains if all of the following are true:

1. A primary is already established by pathology.
2. The morphology of the lesion is compatible with the established primary.
3. The clinical impression is a metastasis.

Sign out

This depends somewhat on the tumour. A synoptic is not done. Margin status should be commented on. A morphologic description is useful if a subsequent resection is done.

Bowel

SMALL BOWEL, RESECTION:
- METASTATIC ADENOCARCINOMA, SEE COMMENT.
- SURGICAL MARGINS NEGATIVE FOR MALIGNANCY.

COMMENT:
The tumour involves only the outer aspect of the bowel wall; the bowel mucosa is
not involved.

The tumour consists of glands with cuboidal tumour cells that have a moderate quantity of
pale cytoplasm, and round nuclei. The tumour is moderately differentiated.

Spine

Pending

VERTEBRAL LESION, L1, BIOPSY:
- ADENOCARCINOMA -- PENDING IHC.

LESION OF T7 VERTEBRA, CORE BIOPSY:
- METASTATIC CARCINOMA, CONSISTENT WITH BREAST PRIMARY, SEE COMMENT.

COMMENT:
The morphology is compatible with a metastatic breast carcinoma.

The tumour cells stain as follows:
POSITIVE: CK7, ER, PR, MAMMOGLOBIN.
NEGATIVE: CK20, TTF-1, CDX2, HER2, GCDFP.

The immunostaining profile is compatible with a metastatic breast carcinoma.

ER, PR and HER2 are interpreted as Class I IHC tests (results used by pathologists),
as per the CAP classification.[1]

1. Am J Clin Pathol 133 (3):354-65.

Micro

Probable lung metastasis

The sections show atypical cohesive cuboidal-to-low columnar cells with moderate nuclear pleomorphism. The nuclei are round/ovoid and eccentrically placed in the cell. Nucleoli of moderate size are identified. Mitotic figures are present. The cytoplasm is lightly eosinophilic and vacuoles are seen focally.

See also

• Cancer.
• Basics.
• Pulmonary lymphangitic carcinomatosis.