Hepatic mesenchymal hamartoma and undifferentiated embryonal sarcoma of the liver: a pathologic review

Figures & data

Figure 1. Pathologic findings of hepatic mesenchymal hamartoma.

Hepatic mesenchymal hamartoma is histologically characterized by (A) a multinodular growth of myxomatous mesenchymal stroma with intervening fibrous septa (hematoxylin & eosin, 4×); (B) each nodule consists of a bland spindle cell proliferation with scattered malformed bile ducts (hematoxylin & eosin, 10×). (C) Some of the nodules demonstrate a florid bile duct proliferation with scattered lymphocytic infiltrate (hematoxylin & eosin, 10×). (D) Entrapped island of hepatocytes (arrow) is occasionally identified in the periphery of the lesion (hematoxylin & eosin, 10×).

Figure 2. Pathologic findings of undifferentiated embryonal sarcoma of the liver.

Undifferentiated embryonal sarcoma of the liver generally shows (A) hypercellular sheets of tumor cells (hematoxylin & eosin, 4×); (B) the neoplastic cells are highly pleomorphic with an increased nuclear to cytoplasmic ratio and hyperchromatic nuclei; tumor giant cells (thick arrow) are frequently identified (hematoxylin & eosin, 10×). (C) The lesional cells are focally elongated/spindled with a loose, myxoid stroma (hematoxylin & eosin, 10×). (D) Necrosis (lower left) is occasionally seen (hematoxylin & eosin, 10×). (E) Mitotic figures (thick arrow) and apoptotic bodies (arrowheads) are readily identified (hematoxylin & eosin, 20×). (F) Eosinophilic hyaline globules (thin arrow), which are PAS-positive and diastase-resistant, may be observed in the neoplastic cell cytoplasm and extracellular matrix (hematoxylin & eosin, 20×).

Table 1. Clinicopathologic characteristics of undifferentiated embryonal sarcoma of the liver and its differential diagnoses.

Diagnosis	Patient demographic	Clinical presentations	Pathologic features	Immunohistochemistry
Undifferentiated embryonal sarcoma of the liver	M = F Age 6–10 years	Abdominal mass, pain, fever and other constitutional symptoms	Sheets of highly pleomorphic tumor cells with myxoid background Brisk mitotic activity Atypical mitoses Eosinophilic globules	Vimentin, CD68, CD56, BCL2, CD10, alpha-1 antitrypsin, cytokeratin (dot-like pattern) and Glypican-3
Hepatic mesenchymal hamartoma	M > F Age <2 years	Enlarged liver mass with respiratory distress due to tumor compression	Lobular growth of myxomatous stroma with branching bile ducts and entrapped hepatocytes	Noncontributory
Hepatoblastoma	M:F = 3:2 Mean age = 19 months	Enlarged abdominal mass, constitutional symptoms, thrombocytosis and elevated serum AFP levels	Different variants resemble stages of liver development	Beta-catenin (nuclear and membranous), Glypican-3 and glutamine synthetase (variable staining pattern in different variants)
Embryonal rhabdomyosarcoma of the biliary tract	F > M Age <5 years	Fever and icteric	Small blue cell tumors with cambium layer underneath the biliary epithelium	Desmin, myogenin and myoD1
Hepatocellular carcinoma	M = F Adults	Abdominal mass with constitutional symptoms; history of chronic liver injury/cirrhosis	Thickened trabeculae with pleomorphic cells (sarcomatoid variant) Intracellular bile and Mallory hyaline bodies	HepPar 1, Glypican-3, AFP, arginase, CD10 (canalicular) and pCEA (canalicular)
Gastrointestinal stromal tumor	M = F Adults	Intra-abdominal mass	Spindle cells with eosinophilic fibrillary cytoplasm	C-kit (CD117), DOG-1 and CD34
Angiomyolipoma	F > M Adults	Intra-abdominal mass	Admixture of thick-walled vessels Spindled to polygonal myoid cells Mature adipocytes	HMB 45, Melan A, desmin, smooth muscle actin
Malignant melanoma	M = F Adults	Primary or metastatic tumor nodules with nonspecific symptoms	Highly pleomorphic neoplastic cells with increased mitotic activity Melanin pigments may be present	HMB 45, MART-1, SOX10 and S-100

F: Female; M: Male.