Hepatic leiomyosarcoma

Hepatic leiomyosarcomas are rare primary malignant tumors derived from smooth muscle cells in the liver.

Epidemiology

Hepatic leiomyosarcoma is rare ¹. An equal sex distribution and a broad age range (5 months-66Y) has been reported. Some have suggested an associated with AIDS ².

Pathology

The tumor may derive from smooth muscle cells of the bile ducts or blood vessels. No underlying etiologic factors are known. Not associated with cirrhosis, but may be related to EBV. C-kit negative (differentiates it from GIST).

Microscopic features

Uniform spindle cells with blunt nuclear ends. Variable mitoses. A few large cells may be noted.

Immunophenotype

Vimentin and desmin positive. 

Radiographic features

CT

• "pseudocystic pattern" with heterogeneous enhancement ³
• commonly large at diagnosis (6-35 cm)
• may be predisposed to rupture/hemorrhage ⁴
• pedunculated leiomyosarcoma has been reported and may arise from the ligamentum teres

MRI

• relatively well-marginated mass
• heterogeneous T2 signal
• intratumoral hemorrhage may result in patchy increase in T1 signal
• slowly increasing enhancement on later postcontrast dynamic phases
• foci of restricted diffusion

PET-CT

• markedly hypermetabolic

Differential diagnosis

• hepatocellular carcinoma
• fibrolamellar hepatocellular carcinoma
• metastatic nonhepatic leiomyosarcoma (e.g. uterus, gastrointestinal, etc)
• fibrosarcoma
• malignant fibrous histiocytoma
• spindle cell hepatocellular carcinoma
• solitary fibrous mesothelioma

Treatment and prognosis

Surgical resection is the standard treatment but with the rarity of the tumor, its effectiveness is uncertain. It had previously been reported that the majority of patients have recurrent tumor and some develop widespread metastatic disease, however, some recent studies suggest that this prognosis was based on some earlier misclassification of GIST tumors as hepatic leiomyosarcomas ^5,7. The clinical course of a pedunculated leiomyosarcoma may be benign ⁶.