Spindle cell melanoma coexisting with chronic lymphocytic leukemia/small lymphocytic lymphoma: a rare collision tumor in multiple sites.

A strong association has been reported between chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) and malignant melanoma (MM). In rare cases of MM, lymphoid malignancies may be detected incidentally during sentinel lymph node biopsies. In this case, we found a unique collision of MM and CLL infiltration in the skin. An 88-year-old male patient presented with a mass on the nasal root. Histopathological examination of the skin biopsy specimen revealed a deeply infiltrative, atypical spindle cell proliferation in the background of a collagenous stroma. Accompanying this lesion, there were foci of monotonous lymphoid cell populations involving skin appendages. In the immunohistochemical studies, the spindle cells were diffusely positive for S100, and focally positive for Melan-A and HMB45; the lymphoid cells were positive for CD20, CD5, and Bcl-2 and negative for CD3, Bcl-6, CD10, and Cyclin D1. Histopathological and immunohistochemical findings were consistent with diagnoses of spindle cell melanoma and CLL. Interestingly, these two tumors together in their same morphological appearance were confirmed in a subsequent liver biopsy. Active skin surveillance of patients with CLL may be important to detect MM at an early stage that correlates with a better prognosis.