Splenic Pathology: Splenic Metastasis |
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Metastatic disease rarely affects the spleen in comparison to other organs,
despite the spleen's large quantity of lymphoid tissue and filtration
of systemic blood flow. Multiple theories have been proposed to explain
the spleen's scarcity of metastatic involvement, though none fully satisfying.
While metastases are rare, it is more common than primary splenic neoplasms.
The incidence of splenic metastasis at autopsy has been reported at 2-8%.
Primary tumors commonly associated with splenic metastasis include lung, breast, melanoma, ovary, and colon, with malignant melanoma being the most common. On
contrast enhanced CT, splenic metastases vary in size from a few millimeters
to several centimeters, but predominately appear as small, hypodense
lesions often with faint peripheral contrast enhancement. This appearance
can easily mimic infections processes and differentiation is made through
a combination of clinical presentation and histopathologic correlation.
Tumors that can develop cystic metastasis, including ovary, breast,
and melanoma, can be difficult to distinguish from splenic cysts. Therefore,
subtle enhancement should be carefully evaluated on contrast enhanced
CT. Peritoneal implants from ovarian, pancreatic and gastrointestinal
tumors may implant on the splenic capsule causing a scalloped appearance.
Calcification may be present in metastasis from mucinous tumors such
as adneocarcinoma of the gastrointestinal tract or cystadenocarinoma
of the ovary.
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