Primary Skeletal Leiomyosarcoma Arising in the Humerus

To the Editor.—We read with great interest the recently published review article by Adelani et al1 concerning the rare presentation of primary leiomyosarcoma (LMS) of extragnathic bone. The authors competently pooled data from almost a hundred well-established cases of primary skeletal LMS in the literature and reported their experience on 3 additional cases discussing aspects of the clinical outcome of this heterogeneous disease. Their observations reinforced the rarity of this pathology primarily affecting the skeletal bones, with only 107 well-documented cases reported in literature to date. To bring additional information, we describe our experience in a case of LMS arising in the humerus. Moreover, some particular cytogenetic findings on this case are also presented.A 53-year-old man, with no remarkable previous medical record, sought medical attention for pain at the left shoulder for about 6 months. At clinical examination no palpable mass or limitation of range of motion was observed. Pain was limited to the upper extremity of the humerus. After 3 months of unsuccessful conservative treatment for a presumed bursitis, imaging investigation revealed a bone lesion. The x-ray images showed a purely osteolytic focal bone lesion in the proximal humeral metadiaphyseal region (Figure, g). The bone lesion lacked marginal sclerosis and computed tomography depicted cortical breakthrough.A biopsy was obtained and histopathologic examination of the specimen showed a densely cellular, moderately differentiated neoplasm, with spindle-shaped nuclei and necrotic foci (25% of specimen), in close relationship to the bone trabeculae, without involvement of the adjacent soft tissue (Figure, a and b). In addition, a fusocellular pattern with brisk mitotic activity (31 per 10 high-power fields) was also present (Figure, c and d). Muscular differentiation was demonstrated by strong and diffuse positivity of the immunoreactions to vimentin, desmin, and α-smooth muscle actin (all Dako Glostrup, Denmark) (Figure, e and f). The final diagnosis was of a high-grade osseous LMS.Initial staging showed no metastatic spread of the disease. Treatment plan was based on total oncologic resection, reconstruction by extracorporeal irradiation and reimplantation associated with a vascularized fibular graft, and adjuvant chemotherapy with doxorubicin and ifosfamide. One year after treatment the patient remains alive with no evidence of disease.Cytogenetic preparations from fresh tumor sample (adjacent to areas verified by frozen section) were obtained as previously described in Brassesco et al,2 and GTG-banding results were interpreted according to the International System for Human Cytogenetic Nomenclature 2005 guidelines.3 Twelve metaphases were analyzed. From these, only 1 presented normal karyotype; the rest exhibited chromosome numbers varying from 46 to 116. Great chromosome heterogeneity was observed. There were no clonal rearrangements except for the constant presence of a large marker chromosome (denoted as mar1) that appeared as 1, 2, or 4 copies (Figure, h). Leiomyosarcomas are most often associated with complex karyotypes with numerous chromosomal gains and losses; however, no consistent aberrations have been noted to date.4The rarity of skeletal LMS and the scarcity of genetic and cytogenetic information on this neoplasm point to the need of gathering international collaborative efforts to better appreciate and hopefully to improve treatment outcomes on primary LMS of extragnathic bone.

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