Spindle Cell Lipoma of the Shoulder: A Case Report

Spindle cell lipoma (SCL), an uncommon variant of benign lipomatous tumor, occurs predominantly in the posterior neck or the shoulders. Patients usually present a well-circumscribed and non-aggressive subcutaneous mass. Histopathologically, the mass comprises fat, CD34-positive spindle cells, and ropey collagen on a myxoid matrix. We report a case of left-shoulder SCL in a 45-year-old Saudi male nonsmoker with no known trauma. A soft tissue mass was seen on MRI near the posterior shoulder. It was a 4.5 cm x 3 cm subcutaneous rounded lump with heterogeneous signal intensity. There is no aggressive or invasive feature, and there is no significant fatty content. The mass was surgically excised with no complication. Histological examination revealed a neoplastic lesion constituted of mature adipocyte lobules and proliferation of loosely held bland spindle-shaped cells against a myxoid background. These cells exhibit neither increased mitoses nor nuclear pleomorphism. There were intervening rope collagen bundles. Lipoblasts and atypical stromal cells are also unidentified. At the periphery, a thin capsule was identified. There is no evidence of malignancy. To the best of our knowledge, this is the first reported case in Unaizah, Al Qassim. The correct diagnosis of SCL without a lipogenic component may be made by paying close attention to the clinical setting, histologic characteristics, immunohistochemical profile, and chromosomal abnormalities.