An 80-year-old man presented with a subcutaneous hard mass. The patient reported the mass developed over a period of 6-8 weeks. Imaging showed a 2 cm mass superficial to the gracilis and involving the greater saphenous vein. The patient underwent surgical resection. Representative images from the resection are shown below.
The correct answer is ...
The correct answer is: Leiomyosarcoma.
Leiomyosarcomas are malignant neoplasms of smooth-muscle cells that typically occur from middle age to older individuals. While the most common site of origin is in the retroperitoneum, leiomyosarcomas often arise from blood vessels, as was seen in this case. A key histologic feature of leiomyosarcomas are intersecting fascicles of spindle cells with abundant eosinophilic cytoplasm. In addition, larger tumors typically demonstrate areas of coagulative tumor necrosis and hyalinized tissue. At the nuclear level, elongated, blunt-ended, cigar-shaped nuclei are readily identified. Nuclear atypia and mitosis are also appreciated with close examination. SMA and desmin stains are positive in most well-differentiated leiomyosarcomas; however, de-differentiated tumors demonstrate focal loss of both stains.
Leiomyomas also demonstrate intersecting fascicles and blunt-ended cigar-shaped nuclei. Important histologic differences that can be used to differentiate leiomyomas from leiomyosarcomas is the lack of nuclear atypia, necrosis, or mitosis, all of which were observed in this case. The presence of any of these features should prompt careful further examination of the specimen, including additional levels, if possible.
Lipomas are benign tumors of mature adipocytes. Grossly, the cut surface of lipomas appears homogenously yellow. Leiomyosarcomas demonstrate a white to tan cut surface and typically will have whorls. The histologic appearance of lipomas is that of mature adipocytes with eccentrically located nuclei.
Malignant peripheral nerve sheath tumors are neoplasms involving the peripheral nerve. These lesions can be sporadic but are often associated with disorder neurofibromatosis type 1. Imaging can be useful in identifying if the lesion is arising from or is associated with a peripheral nerve, unlike the vein, as was seen in this case. Microscopically malignant peripheral nerve sheath tumors demonstrate uniform spindle cells with areas of hyper and hypocellularity.
Blake Ebner, M.D., Ph.D.
Resident, Anatomic Pathology and Neuropathology
Jorge Torres-Mora, M.D.
Consultant, Anatomic Pathology
Assistant Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science