lipomasare slow growing fatty tumours of mesenchymal origin and can occur in any organ of the body . spindlecell lipomas ( scls ) are lipoma variants which have the potential of neuromuscular invasion despite their benign histopathology . this case report highlights a spindle cell lipoma variant in the supraclavicular area found intraoperatively to invade both the paravertebral muscles and the brachial plexus . computerised tomography ( ct ) and magnetic resonance imaging ( mri ) findings were suggestive of possible malignancy but the biopsy and immune - histochemical stains confirmed the diagnosis as scl .        this report highlights the need for making a preoperative diagnosis of spindle cell lipoma . this ensures accurate patient consent and appropriate preoperative surgical planning including surgical approach and extent of surgery . a - sixty - three - year - old gentleman presented with a two - year history of a left supraclavicular mass which had increased in size over the previous three months prior to presentation . he was a smoker with a past medical history of hypertension and type 2 diabetes mellitus .         on examination , there was a large tennis ball sized swelling in the left neck level v area with no palpable cervical lymphadenopathy . fine needle aspiration ( fna ) of the mass was performed but it was nondiagnostic . ct neck showed a 46  69  91  mm left supraclavicular mass posterior to the sternocleidomastoid muscle and superficial to the paravertebral muscles , of fatty density with fine internal septations ( figures 1 and 2 ) . the radiological appearance was suggestive of a lipoma but a low - grade liposarcoma could not be excluded due to the internal complexity confirmed on mri . the case was discussed at the multidisciplinary meeting and due to the suspicion of malignancy , and a nondiagnostic fna , excision biopsy was recommended . the operation was technically difficult because the mass invaginated around the brachial plexus and extended posteriorly through the prevertebral fascia . complete excision of the mass was undertaken with mobilisation and preservation of the brachial plexus . histological examination showed mature adipocytes interspersed with fibrous septa containing bland spindle cells with focal pseudo - angiomatous arrangement . there was the presence of ropey collagen , a very characteristic finding in spindle cell lipoma . no lipoblasts were seen and the spindle cells showed strong uniform immuno - histochemical positivity for cd34 . subsequent review also showed negative staining for cdk4 and p16 , supporting the diagnosis of spindle cell lipoma , and excluding atypical lipomatous neoplasm . spindle cell lipoma ( scl ) is a benign tumour which typically occurs on the posterior neck , shoulder , or upper back in predominantly elderly males . there is a marked male predilection especially in the sixth decade which may be partly explained by androgen receptors reactivity . other rare reported sites of occurrence in the head and neck region include the face , suprasellar region , buccal fat pad , oesophagus , nasal vestibule , the tongue [ 7 , 8 ] , floor of mouth , vallecula   and parotid gland . histologically it consists of a proliferation of mature adipocytes , collagen fibres , and spindle cells within a myxoid stroma ( figure 3 , 4 , 5 , 6 , and 7 ) and can infiltrate between skeletal muscle fibres . on immuno - histochemistry , the spindle cells express cd34 and they are negative for s-100 protein . they are however desmin negative tumours and this may help differentiate them from other cd34 positive tumours . differential diagnoses include atypical lipomatous tumour / well - differentiated liposarcoma , pleomorphic lipoma , neurofibroma , nuchal fibroma , lipoblastoma , hibernoma , cellular angiofibroma , extramammary myofibroblastoma , and solitary fibrous tumour . it is important to note that reactivity to cd34 immuno - histochemical stain is not specific to only spindle cell lipoma as other entities can demonstrate immunoreactivity to cd34 such as atypical lipomatous neoplasm ( aln)/well - differentiated liposarcoma ( wdl ) . aln / wdl is the most common form of liposarcoma seen in late adult life with equal gender affectation generally . they contain a significant component of mature fat and tend to have less well - defined borders than lipomas . the favoured sites for aln / wdl are deep soft tissues of extremities and retroperitoneum compared to scl that favour the subcutis of the posterior neck , back and shoulders . this coupled with the usual absence of giant marker and ring chromosomes that are typically seen in atypical lipomatous tumour / well - differentiated liposarcoma supports their distinction . immunostaining for mdm2 and cdk4 has been shown to be a relatively sensitive and specific means of identifying and separating atypical lipomatous neoplasm / well - differentiated liposarcoma from various benign lipomatous lesions [ 15 , 16 ] .            in this case report , histologic findings did not demonstrate sufficient nuclear atypia to suggest a diagnosis of atypical lipomatous tumour and further immuno - histochemical markers that would make such a diagnosis possible ( cdk4 , p16 ) were found to be negative . scl shares overlapping clinical , morphologic , and immuno - histochemical findings with pleomorphic lipoma as well as the same cytogenetic aberrations . it however typically arises in the dermis , often in younger patients and lacks the characteristic ropey collagen of scl . schwannoma and neurofibroma have a similar striking nuclear palisading and conspicuous mast cell infiltrate present in some scl . scl may also be mistaken for several sarcomas , including myxoid liposarcoma or spindle cell liposarcoma . the presence of multinucleated floret - like giant cells is characteristic of pleomorphic lipoma and is occasionally seen in atypical lipomatous tumour / well - differentiated liposarcoma .             in this case report , the spindle cell lipoma presented a diagnostic and management dilemma as it could not be clinically differentiated from a liposarcoma which would require a more radical approach to treatment . the radiologic findings of a complex internal architecture with fine septations allowed differentiation of the preoperative differential diagnosis from a benign lipoma or possible malignancy but could not differentiate between a liposarcoma or a spindle cell lipoma . the authors suggest that when radiologic findings suggest a complex internal architecture suspicious for a diagnosis of a possible lipomatous tumour , it is imperative to obtain a biopsy prior to definitive surgery . histologic interpretation is crucial and this can be supported by the use of immune - histochemical stains . immuno - histochemical stains demonstrating positivity for cd34 can be helpful in diagnosis of cd34 positive tumours such as spindle cell lipoma , and the differential diagnoses discussed such as atypical lipomatous tumour and dermatofibrosarcoma protuberans ( dfsp ) . as discussed , further differentiation can be made based on clinical presentation , immunoreactivity for actin or desmin , s-100 protein staining of mature lipocytes , the presence / absence of ropey collagen bundles , multinucleated floret - like giant cells and cytogenetic aberrations . in difficult cases , a preoperative diagnosis of spindle cell lipoma is crucial to surgical management as it impacts on the consent process , surgical approach , extent of surgery , and management .         in making a preoperative diagnosis , however , it is important to note that fna may be nondiagnostic as it was in this case , because the specimen consisted largely of fatty cells . core biopsy is preferable and can be obtained by an initial procedure under anaesthesia prior to definitive surgery based on a histological diagnosis . a preoperative diagnosis will guide the consent process as such patients can be warned of the risks of neurovascular injury as well as determining the extent of surgery .