Collision Tumor of Merkel Cell Carcinoma and Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma: A Cytological and Flow Cytometric Diagnostic Pitfall.
Gennaro Acanfora, Vincenza Cerbone, Maddalena Raia et al.
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Case in brief
A 68-year-old male presented with right axillary lymphadenomegaly. Fine-needle cytology revealed a population of intermediate-sized lymphoid cells and larger plasmacytoid cells. Flow cytometry indicated a B-cell population consistent with chronic lymphocytic leukemia/small lymphocytic lymphoma, alongside suspicious plasma cells. Histological examination after lymph node excision confirmed a collision tumor of Merkel cell carcinoma and CLL/SLL, illustrating diagnostic challenges.
What made this case unusual
The case exemplifies a collision tumor of Merkel cell carcinoma and chronic lymphocytic leukemia/small lymphocytic lymphoma within a single lymph node, which is exceptionally rare and poses significant diagnostic challenges.
Diagnostic / clinical pearl
Clinicians should be aware that collision tumors can complicate the interpretation of cytological specimens, particularly when neuroendocrine features are present in lymphoid populations.
Why it matters
Understanding the potential for collision tumors in lymph nodes can prevent misdiagnosis and ensure appropriate management of coexisting malignancies.