Lymphoma mimickers
42-year old female presented with a mass in right axillary region. The biopsy demonstrated that the mass represents a lymph node involved with a neoplasm which was partially necrotic. The neoplastic cells appeared discohesive, pleomorphic, with abundant cytoplasm and prominent nucleoli (Figure 1).

Figure 1:

The second case is a 37-year old woman who was being followed for a malignancy. A tru-cut biopsy was performed from the cervical lymph node which showed that the lymph node architecture was partially altered by neoplastic cells with pleomorphic nuclei and prominent eosinophilic cytoplasm. There was accompanying polymorphonuclear leukocytes and small lymphocytes (Figure 2).

Figure 2:

What is your diagnosis?
PATHOLOGIC DIAGNOSIS
The differential diagnosis for both cases included malignant lymphoma both clinically and morphologically. However, in both cases the immunohistochemical stains showed that the neoplastic cells were negative for LCA, CD20 and CD3. Therefore the immunohistochemical panels were expanded and in the first case the neoplastic cells turned out to be positive for S-100, HMB-45 and MelanA, therefore the diagnosis was metastatic malignant melanoma (Figure 3).

Figure 3:

The second one showed positivity for pan-cytokeratin (Figure 4) and thus was diagnosed as metastatic epithelial neoplasm (primary in nasopharynx).

Figure 4:

CONCLUSION
These two cases stress the importance of immunohistochemical studies in the differential diagnosis of malignant lymphoma and its mimickers.