Anaplastic lymphoma kinase-positive anaplastic large cell lymphoma presenting as a bladder neoplasm.

Malignant lymphoma presenting in the bladder has been classified in primary cases, as the first sign of disseminated disease and as a secondary infiltration. Most of the examples in the literature have been reported as single cases. Reported herein is the case of a 45-year-old man with an anaplastic large cell lymphoma (anaplastic lymphoma kinase (ALK) and granzyme B positive) that presented as a bladder neoplasm. The morphological differential diagnosis was complex because the EMA-positive immunophenotype, CD45 and CD3 negativity and the clinical manifestation simulated a transitional cell carcinoma. It is important to be aware of its existence because a poorly differentiated bladder carcinoma cannot be ruled out if CD30 and ALK immunostaining are not performed. T-cell receptor-gamma clonal rearrangement could be also helpful in these cases. Although bladder involvement by recurrent lymphoma is a sign of widely disseminated disease and it is associated with a very poor prognosis, it seems that chemotherapeutic regimens in this kind of ALK-positive lymphoma could be effective, given that the present patient had an impressive response to chemotherapy treatment.