MPO and CD 117
were negative according to flow cytometry.
The spindle cells were negative for melanin A, HMB-45, epithelial membrane antigen, pankeratin, muscle actin, CD 117
, low-molecular-weight keratin, high-molecular-weight keratin, CD34, CD5, factor VIIIa, and CD45/leukocyte common antigen.
CD 34+ fibrocytes, alpha- smooth muscle antigen-positive myofibroblasts, and CD 117
expression in the stroma of invasive squamous cell carcinomas of the oral cavity, pharynx, and larynx.
Pathologic examination revealed it to be a gastrointestinal stromal tumor (GIST) that had originated in the stomach and was positive in the antibody study for VIM, CD 34, and CD 117 (kit protein).
The CD 117 protein is located in the cell membrane of all cells expressing the kit proto-oncogene.
Mutation of the kit proto-oncogene results in a CD 117 receptor that is constantly stimulated without the presence of the stem-cell growth factor.
Both types of cells express the CD 117 protein, but Cajal cells do not stain for CD 34 nor for other muscle cell antigens frequently seen in GIST cells.
On immunohistochemistry examination, the tumor was found to have CD 117 antigen, which is an established hallmark of GIST.
A partial gastrectomy was performed, and CD 117 was identified in the resected mass.
The diagnosis of seminoma was confirmed by further immunohistochemical studies (figure 2, C), although the negative staining for placental alkaline phosphatase and CD 117
are considered to be atypical for seminoma.