Atypical multivacuolated lipoblasts and atypical mitoses are not compatible with the diagnosis of spindle cell/pleomorphic lipoma

We have read with great interest the recent papers of Michal et al [1,2], describing lipoblasts (including multivacuolated lipoblasts in some cases) and (atypical) mitotic figures in pleomorphic lipomas. We agree with the authors that lipoblasts can be observed in spindle cell/pleomorphic lipomas. In the spindle cell/pleomorphic lipoma chapter of the recent WHO Classification of Tumours of Soft Tissue and Bone, fourth edition, it is stated that "although fat cells typically lack atypia, some spindle cell/pleomorphic lipomas contain atypical adipocytes and lipoblasts, showing morphologically overlap with atypical lipomatous tumours" [3].

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