2 for an ambiguous lesion in a needle biopsy virtually excludes a diagnosis of EAML because it is mostly negative or occasionally displays only focal expression for this keratin.
1,24) However, EAML can be distinguished by the demonstration of other melanocytic antigens (HMB-45) and muscle markers.
The primary differential diagnosis of hepatic EAML is with HCC and epithelioid leiomyosarcoma.
4) Malignant melanomas may rarely lack S100 staining, and in such cases their distinction from EAML depends on additional markers, most notably myoid markers.
Epithelioid GIST, other epithelioid mesenchymal tumors, and epithelioid malignant melanomas are in the differential diagnosis of EAML.
Although immunohistochemistry plays a major role in the differential diagnosis of EAML, extensive sampling of the tumor is also recommended to look for abnormal blood vessels and intratumoral fat (Figure 3, A and B).
A correct diagnosis of EAML may require prudent use of immunohistochemistry (Table).
1-4,8) In contrast to their classical counterpart, EAMLs are now considered a potentially malignant neoplasm.
12) Although the color of classical AMLs varies from yellow to tan, depending on the tissue component, EAMLs are usually grey-tan to white and they may contain areas of necrosis.
Further, less than 40% of EAMLs may have exclusive cytoplasmic S100 staining without nuclear staining, a pattern different from melanomas.
Because AML and EAMLs are associated with TSC, the (germ-line) genetic changes characteristic of TSC will be found in these tumors.