Perivascular Ki-1 + lesions.

We describe three male patients diagnosed by histologic and immunophenotypic criteria to have a Ki-1 + lymphoproliferative disorder. All three cases shared a unique morphologic finding, not previously described: prominent perivascular cuffing of anaplastic/pleomorphic tumor cells around small and medium sized vessels. One case was a Ki-1 + anaplastic large cell lymphoma (ALCL) which developed in the setting of a low grade follicular B-cell lymphoma. A pseudoglandular pattern caused referral for consultation as a possible adenocarcinoma. One case was a cutaneous Ki-1 + lymphoproliferative disorder consistent with lymphomatoid papulosis (LyP). The third case was a cutaneous Ki-1 + ALCL. This study provides evidence that although perivascular cuffing of tumor cells is not frequently seen in Ki-1 + lymphoproliferative disorders (3 of 116 cases in our consultation file), it may be a prominent architectural feature causing confusion with epithelial or mesenchymal tumors. For this reason we recommend inclusion of this feature in the list of architectural features already described for Ki-1 + lymphoproliferative disorders.