Intraoral spindle-cell lipoma with chondroid differentiation : importance in the diagnosis of oral lesions presenting chondroid tissue Lipoma de células fusiformes intraoral com diferenciação condroide : importância no diagnóstico de lesões orais contendo tecido cartilaginoso

Lipomas are benign neoplasms of adipose tissue presenting several histologic variants, which can be rarely found in the oral cavity. We present a case of a 62-year-old woman with a submucous nodule located in the tongue. Histopathological examination revealed an encapsulated tumor composed of myxoid tissue, spindle cells and mature adipocytes in transition to cartilaginous tissue. The final diagnosis was spindle-cell lipoma with myxoid change and chondroid differentiation. No sign of recurrence was found after five years. The diagnosis of intraoral mesenchymal lesions with chondroid differentiation requires careful histologic examination, mainly to differentiate between benign and malignant lesions.


introDuCtion
Lipomas are benign neoplasms of mature adipose tissue, most commonly found in areas where adipose tissue is present, above all in the subcutaneous or submucous regions.They are somewhat rare in the oral region, representing about 1% to 4% of all cases (1) .Lipomas often present as a slow-growing mass, almost always asymptomatic (2) .Their most common location in the oral region is the buccal mucosa, followed by floor of the mouth, tongue and lips (1,2) .
Mesenchymal differentiation of lipomas into bone and cartilage is a rare event (2,5) .Chondroid lipoma is the main variant presenting chondroid tissue, with features of both embryonal fat and embryonal cartilage, and its recognition is important because it can be morphologically similar to sarcomas, particularly myxoid liposarcoma and myxoid chondrosarcoma (6) .
In order to avoid misclassification of different histological types of lipoma, spindle-cell lipoma with cartilaginous differentiation must be distinguished from chondroid lipoma.To the best of our knowledge, only two cases of spindle-cell lipoma with chondroid tissue have been published in the English language literature.Therefore, the purpose of this article is to report a case of spindlecell lipoma with cartilaginous differentiation affecting the tongue, emphasizing the distinction between these lipomas and chondroid lipoma or other tumors with chondroid tissue.
A 62-year-old woman was referred for evaluation of a tongue nodule that had been present for about six months.Her medical history and systemic review were not significant.The patient had no history of trauma in the region.Physical intraoral examination revealed a painless well-delimited submucous nodule, firm on palpation, measuring about two centimeters in diameter noted on the left lateral border of the tongue (Figure 1).The main diagnostic consideration was a benign neoplasm, including salivary gland tumors or mesenchymal neoplasms such as lipoma, granular cell tumor, neurofibroma, schwannoma or ectomesenchymal chondromyxoid tumor.According to these hypotheses, an excisional biopsy was indicated.During surgery, a well-circumscribed yellowish mass was found.On gross examination the lesion did not float on formaldehyde.On microscopic examination, the lesion consisted of an encapsulated tumor with myxoid areas admixed with spindle and stellate cells and mature adipocytes in transition to cartilaginous tissue, which displayed well-differentiated areas preferentially located in the central portion (Figure 2).Immunohistochemical stains for S100 protein were positive in the adipocytic cells and cartilaginous tissue, and CD34 was found in spindle cells of the myxoid areas (Figure 3).Based on these histopathological and immunohistochemical features, a diagnosis of spindle-cell lipoma with prominent myxoid change and chondroid differentiation was rendered.No recurrence was identified during a five-year follow-up period.

DiSCuSSion
Lipomas are the most common benign soft tissue mesenchymal tumors, and several microscopical variants have been reported, including fibrolipoma, angiolipoma, myolipoma, sialolipoma, osteolipoma, spindle-cell/pleomorphic lipoma and chondroid lipoma.Spindle-cell lipoma is an uncommon variant, first reported by Enzinger and Harvey in 1975 (7) .Microscopically, it is composed of mature fat cells, collagen-forming spindle cells with immunoreactivity for CD34 in a fibrocollagenous and myxoid background (7,8) .Some cases of spindle-cell lipoma show prominent myxoid changes (9) .Spindle-cell lipoma accounts for approximately 1.5% of all adipocytic neoplasms (10) , and typically occurs in elderly men as a solitary lesion in the posterior neck and back (11) .It is less commonly found in the oral cavity (12,13) .Searching in the literature for reported cases of oral spindle-cell lipomas, we found 37 cases, which are summarized in the Table.From these 37 cases, 20 were situated in the tongue, followed by five cases on the floor of the mouth.Patients' mean age was 57.4 years, ranging from 23 to 88 years.Our case also affected the tongue of the 62-year-old woman, and the microscopic features were compatible with spindle-cell lipoma with prominent myxoid changes and chondroid differentiation.in vacuolated cells.Chondroid lipoma should be distinguished from chondrolipoma, which is a lipoma with cartilaginous metaplasia.In chondrolipomas there is absence of lipoblasts and myxoid matrix, and a clear separation between the cartilaginous tissue and the fatty component (5) .Cases of chondrolipomas have also been reported in the intraoral region (35)(36)(37)(38)(39) .Our case does not represent a chondroid lipoma, due to lack of lipoblast-like cells.The presence of chondroid tissue in spindle cell lipoma is very uncommon.Lau et al. (2015) (30) reported eight cases of spindlecell lipoma of the tongue, and they found two cases containing a tissue imparting chondroid appearance.
The presence of cartilaginous tissue within a lipoma is a relatively rare finding (5) .Chondroid lipoma and chondrolipoma are the main variants that exhibit chondroid tissue formation.Chondroid lipoma is a rare variant, mainly in the head and neck region, and was included in the World Health Organization (WHO) classification of soft tissue tumors in 2002 (3) .Microscopic examination of chondroid lipomas shows mature nests of vacuolated lipoblasts, in a prominent myxoid to hyalinized chondroid matrix, and a variable amount of mature adipose tissue.The tumor is usually circumscribed by a fibrous capsule and there is no cell atypia or mitotic figures (32)(33)(34) .Chondroid lipomas may show positivity for vimentin, S100 protein (in lipoblasts), and CD68 Intraoral spindle-cell lipoma with chondroid differentiation: importance in the diagnosis of oral lesions presenting chondroid tissue rESuMo Lipomas são neoplasias benignas de tecido adiposo que podem apresentar diversas variantes e raramente são encontradas na cavidade oral.Apresentamos o caso de uma mulher de 62 anos de idade com queixa de um nódulo na língua.A análise histopatológica da lesão revelou tumor encapsulado composto de tecido mixoide, células fusiformes e adipócitos maduros em transição para tecido cartilaginoso.Nenhum sinal de recorrência foi observado após acompanhamento de cinco anos.O diagnóstico de lesões mesenquimais intraorais contendo diferenciação condroide requer atenção especial, principalmente para a diferenciação de lesões benignas e malignas.Unitermos: lipoma; diagnóstico; microscopia; cartilagem.by a multinodular architecture, abundant myxoid matrix, and malignant chondroblast-like cells (45) .Lipomas with chondroid differentiation may be confused with this malignant neoplasm rEfErEnCES

figurE 1 −figurE 3 −
figurE 1 − Submucous nodule on the left lateral border of the tongue

taBLE −
Summary of spindle-cell/pleomorphic lipoma of the oral region reported in the English-language literature