Cytokeratin positivity in anaplastic large cell lymphoma: a potential diagnostic pitfall in misdiagnosis of metastatic carcinoma

Abstract

Cytokeratin (pan) and epithelial membrane antigen (EMA) were considered as commonly useful epithelial markers to distinguish cancer from lymphoma, but the expression of cytokeratin (pan) and EMA had also been seen in some lymphomas. Here, we presented an unusual case of anaplastic large cell lymphoma (ALCL) absence of some lymphoid markers (Including CD3, CD20, Pax-5, CD45Ro) and positive for cytokeratin (pan) and EMA, which was misdiagnosed as metastatic carcinoma. Our case suggested that the epithelial markers (including cytokeratin and EMA) show an overlap with that of ALCL, which represented a diagnostic pitfall for confusing ALCL with metastatic carcinoma.

Keywords: Anaplastic large cell lymphoma; anaplastic lymphoma kinase; immunohistochemistry.

Figure 1

Hematoxylin and eosin staining. A. The normal structure of lymph node is destroyed and replaced by nests of infiltrating tumor cells (hematoxylin-eosin, original magnification ×50). B. The tumor cells presented some similar characteristics of carcinoma cells. (hematoxylin-eosin, original magnification ×100). C. The tumor cells showed in a patchy distribution and exhibited typical hallmark cells (hematoxylin-eosin, original magnification ×200). D. Showed the tumor cells infiltrates lymph node sinuses. (hematoxylin-eosin, original magnification ×100).

Figure 2

Immunohistochemical analysis. A. The tumor cells were positive for cytokeratin(pan), roblastic reticulum cells showed a typical dendritic shape (Original magnification ×100). B. High magnification showed that positive reactivity of cytokeratin(pan) with Golgi-associated dot-like staining pattern. (Original magnification ×200). C. The tumor cells were negative for CD3, but T lymphocytes showed a nuclear staining (Original magnification ×100). D. CD20, E. Pax-5 were also negative in atypia tumor cells and positive for B lymphocytes. (Original magnification ×100). F. showed the high Ki-67 labeling index. (Original magnification ×100). G. The large lymphocytes are strongly CD30 positive with a membrane and Golgi pattern of staining. (Original magnification ×100). H. ALK/P80 immunohistochemistry shows strong cytoplasmic staining in the neoplastic cells. (Original magnification ×100).