Diagnostically Challenging Spindle Cell Lipomas: A Report of 34 “Low-Fat” and “Fat-Free” Variants

Department of Anatomic Pathology, Cleveland Clinic, Cleveland, OH 44195, USA.
American Journal of Dermatopathology (Impact Factor: 1.39). 10/2007; 29(5):437-42. DOI: 10.1097/DAD.0b013e31813735df
Source: PubMed


Spindle cell lipomas (SCL) classically occur as subcutaneous masses in the upper trunk/neck of older men and are composed of mature fat, CD34-positive spindled cells, ropey collagen, myxoid matrix, and blood vessels. A number of variants have been reported, including SCL with pseudoangiomatous change, composite SCL hibernoma, and composite SCL/pleomorphic lipoma. A review of over 300 consultation cases diagnosed as SCL revealed 34 cases in which fat was noted to be present in <5% of the tumor (n = 30) or absent (n = 4). These cases posed diagnostic difficulties because of the dearth of fat; we propose the terms "low-fat" and "fat-free" SCL for these variants. The tumors presented in older men (mean, 56 years; ratio of males to females, 11:1) and presented as small (mean, 2.0 cm) circumscribed dermal or subcutaneous masses of the head/neck (n = 18), back (n = 7), shoulder (n = 5), leg (n = 2), arm (n = 1), or unknown location (n = 1). In the majority, referring pathologists considered benign diagnoses, usually benign nerve sheath tumors, but in four cases low-grade sarcoma was considered. In only three cases was SCL considered. The tumors were composed of aggregates of CD34-positive, bland spindled cells arranged in characteristic parallel arrays, admixed with ropey collagen and myxoid matrix. Isolated clusters or single adipocytes were present in 30 cases; four were devoid of fat. CD34 was diffusely positive (10/11). A high index of suspicion based on clinical context and identification of other typical features of SCL are key features to the diagnosis of low-fat and fat-free SCL.

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Available from: Steven D Billings, Oct 03, 2015
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    • "Although the histopathological features suggested the diagnosis of pleomorphic lipoma, it remained challenging because of the lack of a fat component. Recently, Sachdeva [11] and Billings [18] reported the ‘low-fat’ and ‘fat-free’ variants of pleomorphic lipoma and spindle cell lipoma, respectively. Meanwhile, they proposed that the key to the diagnosis of such variants lies in the nonlipogenic component rather than the lipogenic component. "
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    ABSTRACT: Pleomorphic lipoma is a rare neoplasm that predominantly occurs in the dermis or subcutis of the posterior neck, upper back, and shoulders. Although pleomorphic lipoma is a benign tumor, it may contain atypical cells. As a variant of spindle cell lipoma, pleomorphic lipoma clinically presents as a slow-growing and well-circumscribed subcutaneous mass. Rarely, some patients have multiple lesions. Histologically, pleomorphic lipoma is composed of mature fat, bland spindle-shaped mesenchymal cells, and coarse 'rope-like' collagen bands. In addition, lipoma contains multinucleated floret-like giant cells. Although spindle cell lipoma/pleomorphic lipoma with little fat was seen in the original series described by Enzinger and Harvey, cases with little to no fat remain diagnostically challenging. Herein, we report a case of 'fat-free' pleomorphic lipoma occurring in the upper back and axilla simultaneously. Although the lipoma was typically composed of bland spindle-shaped cells, rope-like collagen, scattered floret-like giant cells, and striking stromal myxoid change in the background, mature fat was absent. Immunohistochemical analyses showed positive staining for CD34, vimentin, and Bcl-2, and negative staining for S100, confirming the diagnosis of pleomorphic lipoma.
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    ABSTRACT: Spindle cell lipoma (SCL) typically occurs in elderly men as a solitary lesion in the posterior neck and back, but less commonly also involves the oral cavity. Here, we describe a rare case of bilateral multiple SCLs of the tongue. The patient was a 72-year-old Japanese man with multiple painless soft nodules in the bilateral margins of the tongue. The patient was not obese, and had used alcohol moderately for more than 40 years. A clinical diagnosis of multiple tongue lipomas was made. The tumors were resected surgically, and they exhibited the histopathological features of SCL, composed of mature fat cells, collagen-forming CD34-positive spindle cells, and sparse mast cells. This suggests that differential diagnosis of intraoral multiple lipomatous nodules should include not only lipomatosis but also multiple SCLs, notwithstanding the rare incidence of the latter.
    Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 08/2008; 106(2):264-9. DOI:10.1016/j.tripleo.2008.02.026 · 1.46 Impact Factor
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