LAUSR

To the Editor: Malignant rhabdoid tumor (MRT), regardless of its primary site, is one of the most aggressive and least therapeutically responsive neoplasms of childhood.1 The study by Kohashi et al proposes to remake the pathologic classification of MRT in children into three groups: ‘conventional-type tumors resembling MRT, atypical teratoid/rhabdoid-type tumors (ATRT) resembling ATRT and small cell-type tumors resembling malignant lymphomas’.2 All of the tumors, as expected, had complete loss of SMARCB1/INI2 expression. There was an equally dismal prognosis among the three groups. What the authors have demonstrated is that MRT is a tumor whose morphologic features can vary from those neoplasms with the typical, widespread presence of classic rhabdoid cells to those cases with variant features, including a paucity of rhabdoid cells and even a small cell pattern. Those rhabdoid filamentous inclusions in the cytoplasm may not be apparent, but the enlarged, vesicular nucleus and prominent nucleolus are major clues to the diagnosis. From the morphologic perspective, the authors have effectively conveyed the important message that the MRT is more than an epithelioid, round-cell neoplasm. Rather than a reclassification, the pathologist must be aware of the fact that the MRT in the kidney, liver, skin, or anyone of its various other sites of clinical presentation may not resemble the idealized mind eye’s images.3 The argument for a reclassification in this study has certain tautologic attributes.