Atypical Pleomorphic Lipomatous Tumor

Abstract

Atypical spindle cell/pleomorphic lipomatous tumor Definition Atypical pleomorphic lipomatous tumor is a low-grade adipocytic neoplasm with a pleomorphic lipoma-like appearance, but with atypical morphologic features (including atypical spindle cells, pleomorphic (multinucleated) cells, pleomorphic lipoblasts, and poor circumscription). This tumor shows important overlapping morphologic and genetic features with the atypical spindle cell lipomatous tumor, suggesting atypical pleomorphic lipomatous tumor and atypical spindle cell lipomatous tumor belong to the same spectrum ("atypical spindle cell/pleomorphic lipomatous tumor") (Creytens et al. 2017; Mariño-Enriquez et al. 2017).

Fine needle aspiration of spindle cell lipoma—Lochkern cells as a clue for diagnosis: A case arising in the parotid gland

“…Another confusing finding can be multinucleate giant cells with hyperchromatic nuclei arranged in a wreath-like fashion (floret cells) as can be found in "pleomorphic lipoma," which is considered in the WHO classification to be a morphologic variant of SCL. 2,7 In addition, the WHO classification includes "atypical spindle cell/ pleomorphic lipomatous tumor" which is a benign adipocytic neoplasm with ill-defined tumor margins containing atypical cells in the absence of necrosis, but no risk for dedifferentiation. 7 The atypical cells in these lesions can lead to an erroneous diagnosis of malignancy, and this difficulty increases when the lesion is outside of the usual locations for SCL.…”

“…2,7 In addition, the WHO classification includes "atypical spindle cell/ pleomorphic lipomatous tumor" which is a benign adipocytic neoplasm with ill-defined tumor margins containing atypical cells in the absence of necrosis, but no risk for dedifferentiation. 7 The atypical cells in these lesions can lead to an erroneous diagnosis of malignancy, and this difficulty increases when the lesion is outside of the usual locations for SCL. 4 A valuable clue to the diagnosis on FNA in our case was the presence of Lochkern cells.…”

“…[3][4][5][6] Moreover, the classic three components of bland spindle cells, mature adipocytes, and ropy collagen bundles of SCL can vary in proportion, producing morphological subtypes of SCL such as fat-poor (little or no fat cells), myxoid (abundant myxoid stroma), and pseudoangiomatous (intratumoral vascular-like space formations) making a cytologic diagnosis even more problematic. 7 Failure to recognize this benign tumor on cytology could lead to a diagnosis of a more aggressive adipocytic neoplasm, such as one of the subtypes of liposarcoma. 8 In this report, the authors present a case of SCL arising in the left parotid gland of a 75-year-old male.…”

Emerging Entities and New Diagnostic Markers for Head and Neck Soft Tissue and Bone Tumors

“…Atypical spindle cell/pleomorphic lipomatous tumor is a recently described adipocytic neoplasm included in the fifth edition of the World Health Organization (WHO) Classification of Soft Tissue and Bone Tumours 13. It only rarely arises in the head and neck, affecting the soft tissues of the neck and face, and less frequently the larynx/hypopharynx 14,15.…”