Merkel cell carcinoma in a patient with B-cell chronic lymphocytic leukemia treated with cladribine and rituximab

Merkel cell carcinoma (MCC) is an uncommon, neuroendocrine skin tumor with an aggressive clinical course. The etiology of the disease is unknown, although sun exposure and immunosuppression may play a role in its development. Coexistence of MCC with chronic lymphocytic leukemia (CLL) is extremely rare and to our knowledge it has been previously described in only 8 patients. We report a 51-year-old woman who presented with a red lump on the right cheek diagnosed as MCC. She had been diagnosed as having CLL 3 years earlier and was treated with 4 courses of cladribine (2-CdA) and subsequently with 4 courses of 2-CdA combined with rituximab. MCC was diagnosed on the basis of histological and immunohistochemical evaluation 2 months after the last course of 2-CdA and rituximab. Surgical excision with tumor-free margins was performed and local adjuvant radiotherapy was applied. Histopathological and immunohistochemical evaluation of the cervical lymph node specimens showed monotonous and diffuse infiltrate of small CD5+, CD20+, CD23+ lymphocytes and no MCC cells were present. To our knowledge, this is the first reported case of MCC occurring in CLL patients soon after treatment with 2-CdA and/or rituximab. The development of MCC in our patient may suggest that this complication rarely observed in CLL patients may have a link with strongly immunosuppressive therapy with 2-CdA and rituximab.