Primary Pleomorphic Omental Rhabdomyosarcoma in an Adult: A Report of a Unique Case

Abstract

Rhabdomyosarcoma (RMS) is a very rare, highly malignant neoplasm thought to originate from the pluripotent mesenchymal tissue. Predominantly diagnosed among children and teenagers, however they can also be encountered in adults. There are a few risk factors associated with RMS like family history of malignancy and genetic syndromes like neurofibromatosis type 1, Li-Fraumeni syndrome, Noonan syndrome and Beckwith-Wiedemann syndrome; however, most cases of RMS are sporadic. Other factors like radiotherapy for other malignancy and pre-natal radiation exposure also are associated with increased risk of developing RMS. The most common reported sites for RMS are head, neck, trunk, pelvis and lower limbs. Omental involvement of primary RMS has been rarely reported in the literature. Principally, the survival of treated RMS cases has improved, primarily due to multidisciplinary management approaches. In this paper, we report a case of primary pleomorphic RMS in a 50-year-old female who presented with abdominal pain.

Keywords: chemotherapy; omentum; pleomorphic rhabdomyosarcoma; primary rhabdomyosarcoma; radiotherapy.

Figure 1. Computed tomography scans with contrast enhancement demonstrating the ill-defined enhanced soft tissue tumour noted posterior to the right anterior abdominal wall (red arrow indicates tumour).

Figure 2. : Magnetic resonance imaging abdomen with contrast enhancement demonstrating the ill-defined enhanced soft tissue tumour noted posterior to the right anterior abdominal wall (yellow arrow indicates tumour).

Figure 3. Macroscopic view of the excised anterior abdominal wall tumour measuring 11 × 9 × 7 cm with segment of ascending colon (red arrow points to a resected segment of ascending colon).

Figure 4. (a, b) H&E: Fragments of high-grade malignant mesenchymal tumour composed of densely cellular fascicles of spindle cells and tumour cells are seen. (c) Desmin positive expression. (d) CD56 positive expression. (e) Myogenin positive expression.

H&E: haemotoxylin and eosin.