Case 12 -

Embryonal Sarcoma Linda D. Ferrell, M.D. Wendy L. Frankel, M.D.

Clinical findings: 23 year old woman presented with 40 lb unintentional weight loss, abdominal fullness, and non-specific abdominal pain. Abdominal CT demonstrated a hepatic neoplasm, and at surgery, a greater than 10 cm hemorrhagic and necrotic mass was found. Case 12 - Figure 1 - Proliferation of spindled and stellate cells, low power Case 12 - Figure 2 - Spindled and stellate cells with ill-defined cell borders and rare multinucleated giant cell, high power Case 12 - Figure 3 - Epithelioid cells, low power Case 12 - Figure 4 - Epithelioid atypical cells containing hyaline globules (arrow) within the cytoplasm and stroma, PAS stain with diastase, high power Pathologic findings: Proliferation of spindled and stellate cells, low power. Spindled and stellate cells with ill-defined cell borders and rare multinucleated giant cell, high power.Epithelioid atypical cells containing hyaline globules within the cytoplasm and stroma, PAS stain with diastase, high power. Diagnosis- Embryonal Sarcoma Comments Undifferentiated (Embryonal) sarcoma Clinical Features. Embryonal sarcoma is a rare tumor that typically occurs in children between the ages of 6 and 10, with some occurring in a slightly older age group (under the age of 20). The presenting features are often that of a mass or of abdominal pain. Complete surgical excision generally offers the best outcome. Gross findings. Embryonal sarcomas are usually large, soft tumors, with a variably cystic and solid areas and a white, shiny or gelatinous or mucoid surface. Additional areas of necrosis and hemorrhage are often present. Microscopic findings. These tumors contain a mixture of spindled and stellate cells embedded in a myxoid stroma. The tumor cells have a granular to bubbly, light pink cytoplasm, and many contain cytoplasmic globules of various sizes which are PAS-digest-positive. These globules may also be noted in the stroma. Other cellular features include the presence of other large atypical tumor cells with hyperchromatic nuclei as well as multinucleated tumor cells. The surrounding stroma is usually myxoid but some dense collagen deposits can be present. Mitotic figures are usually numerous. Hematopoeisis is often noted and entrapped hepatocytes and/or ductules can be present at the tumor's periphery. Special studies. The tumor cells of the lesion have been shown to immunohistochemically stain for vimentin, alpha-1 antitrypsin, alpha-1 antichymotrypsin. Mesenchymal Hamartoma Clinical features. Mesenchymal hamartoma (MH) is a benign tumor which occurs primarily in young children, predominantly presenting at less than 2 years of age. It is the third most common tumor of the liver in this age group (following hepatoblastoma and infantile hemangioendothelioma). The patient often presents with such clinical symptoms as a palpable liver mass, abdominal enlargement, or respiratory distress due to compression by the tumor. No risk for malignant transformation has been noted. Gross findings. The tumor can be solid or cystic, with the solid areas of this tumor typically a tan color. When cysts are present, they contain a translucent fluid or a gelatinous material. These cysts may form due to the degeneration of the loose mesenchymal tissue of the tumor, and it is thought that the tumor probably enlarges by continued accumulation of fluid into these cysts. Microscopic features. MH has epithelial and stromal components. The former consistent of relatively normal-appearing hepatocytes and bile ducts, both which are surrounded by varying amounts of myxoid to fibrous stroma. The hepatocytes are cytologically unremarkable and are arranged for the most part either in small clusters or in larger groups with retention of the cell plate architecture as in the normal liver. The bile duct structures are typically arranged in a branching pattern, and often are associated with an acute inflammatory infiltrate in the duct walls or adjacent to it. The cystic spaces, when present, may be lined by flattened to cuboidal epithelial cells, which are surrounded by a loose to dense fibrous tissue. Cysts may also lack any lining cells. The stroma generally contains increased numbers of small vascular structures (but the cysts are not lined by endothelial cells), spindle cells, and inflammatory cells. No normal portal zones are present. Extramedullary hematopoiesis is often noted. Infantile Hemangioendothelioma Clinical features. The infantile hemangioendothelioima (IHE) is the second most common tumor in children under three years of age, second only to hepatoblastoma, and almost all the reported cases have occurred in infants less than six months old. The tumor is almost twice as common in girls than in boys. The tumors are often multifocal within the liver and about 10% of the patients also have hemangiomas present in other organs. The tumors may also be associated with other congenital anomalies, such as bilateral renal agenesis, Beckwith-Wiedemann syndrome, hemihypertrophy, and meningomyelocele. The clinical presentation may be an abdominal mass or distention (with hepatomegaly), jaundice, diarrhea, constipation, vomiting, congestive heart failure, or failure to thrive. Other less common findings can include thrombocytopenia due to sequestration of platelets within the tumor(s) or rupture with hemoperitoneum. These tumors are generally benign histologically, but because of their multifocality and/or large size, the patients have a high mortality rate due to cardiac or hepatic failure. The tumors can regress, but therapy such as resection, embolization, hepatic arterial ligation, or chemo/radiation is often necessary for patient survival. Angiosarcoma may rarely arise in this lesion. Gross findings. IHE is often a poorly circumscribed lesion, and can be solid and cystic, with variable hemorrhagic foci. These foci typically alternate with the fibrotic (solid) zones. The tumors are multifocal. Microscopic findings. Two histologic subtypes have been described for this lesion, although practically speaking, distinguishing the two can be difficult. Type 1 is defined by a mixture of large numbers of small vascular channels and fewer, large, irregularly shaped spaces with a cavernous appearance, with both types of vascular channels lined by a single layer of endothelial cells. The vascular spaces are separated by a poorly-developed stroma with only scattered collagen or reticulin fibers. Small bile ducts and well as hepatocytes can be seen in the stroma as well, often near the periphery of the tumor. Focal necrosis, hemorrhage, fibrosis, and calcification are often present. Type 2 lesions contains endothelial cells with more atypical cytologic features, with mitotic activity and hyperchromasia, and arranged in a more complex budding or branching pattern [Craig, 1989 #396] than noted in type 1 lesions. Special studies. The endothelial cells of the tumor will stain with CD34, CD31, and Factor VIII. The stromal cells underlying the basement membrane of the capillary structures are alpha-smooth muscle actin and HHF35 positive, desmin negative, a profile consistent with pericytes. References Abbassi V, Hoy G, Weintraub B: HCG production by hepatoblastoma causing isosexual precocious puberty. Pediatric Research 13:375-381, 1979. 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