Oral Spindle Cell Lipoma in a Rare Location: A Differential Diagnosis

Spindle cell lipoma (SCL) is an uncommon and histologically distinct variant of lipoma. It usually occurs as a solitary, subcutaneous, and well-circumscribed lesion in the posterior neck, shoulders, and back of older men. SCL of the oral cavity is rare. We present the clinical-pathologic features of the third case of SCL located on the hard palate and discuss the histological differential diagnosis with other fusiform neoplasms.

A 56-year-old man was evaluated for an asymptomatic swelling on the right side of the hard palate. The intraoral examination showed a 25×20 mm sessile and circumscribed tumor, underlying an apparently healthy mucosa of normal color. The lesion revealed a floating consistency during palpation. Excisional biopsy was carried out based on a clinical diagnosis of lipoma or a benign minor salivary gland tumor. The histopathology demonstrated a well-circumscribed but unencapsulated proliferation of bland spindle cells admixed with mature adipocytes in a collagenous/myxoid stroma. The spindle cells were uniform, exhibiting elongated nuclei and narrow cytoplasmic processes without atypia. They were positive to CD34 and negative to factor VIII, alpha-smooth muscle actin, S100, cytokeratin, and actin. Mitotic activity was low, as confirmed by Ki-67 immunostaining. No lipoblastic activity was found. The diagnosis of SCL was therefore established.

Oral spindle cell lipoma is a rare benign lipomatous tumor. The histologic picture shows a range of variations and the observation of morphological features is important to distinguish this lesion from other fusiform tumors. Immunohistochemistry should be helpful in this differentiation.