A 65-year-old man came to our observation with a solid-elastic mass of about 4.5 cm maximum diameter on the proximal region of the left forearm, ulnar side, that appeared hypomobile on the underline planes. He reported being affected by this "bump" for at least 20 years, but it had recently shown a rapid growth. Furthermore, he reported having already undergone another excision in local anesthesia after an ultrasound examination about 1 year before at another hospital. An X-ray of the forearm showed a soft tissue mass with irregular calcifications (Fig. 1) and CT scan of the limb confirmed this finding. Magnetic Resonance Imaging (MRI) showed a soft tissue mass arising in the subcutis and involving the skin and the subfascial and muscular planes, with partial invasion of wrist and fingers flexor muscles and partially surrounding the bone (lateral side of the ulna). The mass was isointense to muscle in T1-weighted sequence (Fig. 2a), hyperintense on T2-weighted sequence (Fig. 2b), with contrast medium enhancement on T1-weighted sequence (Fig. 2c) and highly vascular (Fig. 3). Staging exams (total body Computed Tomography scan and Positron Emission Tomography scan), showed no other tumor localizations.
After preoperative needle biopsy, surgical excision of the tumor was performed, including skin (with the scar of the previous surgery), fascia, muscles and a portion of the ulna. Reconstruction was performed with plate, screws and cement and coverage with a microsurgical rotation flap.
Gross examination of the surgical specimen revealed a solid white neoplasm with a maximum diameter of 6 cm in the soft tissues. Histologically, the tumor showed two different, abruptly separated components (Fig. 4). One consisted of a proliferation of atypical spindle or ovoid cells with cigar-shaped nuclei and eosinophilic cytoplasm arranged in long interlacing fascicles, an appearance consistent with leiomyosarcoma (Fig. 5). The other component consisted of atypical pleomorphic cells producing osteoid matrix in disorganized trabeculae with focal calcification (Fig. 6). Areas of cartilage matrix production were identified as well.
Immunohistochemically, areas with leiomyosarcomatous appearance were strongly positive for alpha smooth muscle actin (Fig. 7a) and desmin (Fig. 7b), whereas the osteosarcomatous component was negative. Both components were negative for cytokeratins (AE1/AE3 and CAM5.2), EMA, S100 protein, CD34 and CD31. SATB2, a marker of osteoblastic differentiation was positive only in the osteosarcomatous component, whereas leiomyosarcoma areas were negative (Fig. 7c, d).
The final diagnosis was leiomyosarcoma grade 2, according to the French Federation of Comprehensive Cancer Centers (FNCLCC) grading system with areas of high-grade osteosarcoma (so-called dedifferentiated leiomyosarcoma). The tumor infiltrated the dermis, the subcutis and the striated muscle. Surgical margins were free of tumour. The review of the histologic slides from the previous surgical excision showed similar histological aspects, although the tumor consisted mainly of leiomyosarcoma with a very limited osteosarcomatous component.
After the surgical treatment, the patient received three cycles of high-dose adjuvant chemotherapy with adriamycin and iphosphamide and local sequential radiotherapy (66 Gy). After an interval of 15 months, MRI showed multiple local recurrences at the site of previous excisions and a PET CT total body scan highlighted bilateral pulmonary nodules, for which he underwent a new cycle of chemotherapy with gentamicin. The patient died after 23 months from presentation due to the progression of the disease.