A Rare Case of Spindle Cell Rhabdomyosarcoma of the Diaphragm in Adult with Thoracoabdominal Extension

Abstract

Rhabdomyosarcoma (RMS) is an uncommon malignant soft-tissue tumor, with diaphragmatic spindle cell RMS being extremely rare in adults. A 41-year-old male patient had progressive breathlessness and right-sided pleuritic chest pain. Imaging and biopsy that includes X-ray, computed tomography, magnetic resonance imaging, histopathology, and immunohistochemistry established a large thoracoabdominal spindle cell RMS. Early diagnosis, careful imaging, and combined treatment were important, and they helped increase knowledge of this unusual entity.

INTRODUCTION

Rhabdomyosarcoma (RMS) is a rare and aggressive soft tissue malignant tumor of mesenchymal origin, which is characterized by skeletal muscle differentiation features.[1] Although RMS is the most frequent soft tissue sarcoma in children and adolescents, its presentation in adults is exceedingly rare and represents <3% of all instances.[1] Such rarity in adults tends to complicate diagnosis and can lead to delayed treatment. Of the several histologic subtypes, one of the most characteristic is the spindle cell variant, initially identified by Cavazzana and colleagues in 1992. It consists of elongated, spindle-shaped tumor cells in fascicles and expresses immunoreactivity to markers of skeletal muscle, facilitating correct histopathological diagnosis.[2] This variant is typically of a more favorable prognosis than other RMS subtypes when identified at an early stage.

Primary tumors of the diaphragm are themselves very rare, and the vast majority of the few which have been reported are benign. Diaphragmatic malignant tumors, in the form of rhabdomyosarcomas, are very rare.[3] Even more rare are those cases in which the tumor crosses both thoracic and abdominal cavities, with severe diagnostic, surgical, and therapeutic difficulties. This broad spectrum of involvement can lead to complex clinical presentations, such as respiratory compromise, abdominal pain, or nonspecific systemic complaints, further obfuscating the early diagnosis. RMS is classically divided into four histological subtypes: pleomorphic, alveolar, botryoid, and embryonal, the most frequent of which in pediatric patients is the embryonal subtype. Involvement of the head and neck area and the urogenital tract is frequent, with diaphragmatic involvement rarely reported.[4,5,6] We report herein a new case of spindle cell RMS from the diaphragm with contiguous thoracoabdominal extension in an adult patient.

This case discloses not only the clinical presentation and radiologic presentation but also the histopathologic and immunohistochemical findings. In presenting this experience, we aim to contribute to the limited literature for this rare entity and bring to light its diagnostic pitfalls, potential complications, and modalities of treatment for future similar presentations.

CASE REPORT

A 41-year-old man came to the casualty with worsening shortness of breath and pleuritic right chest pain over few weeks. Patient had no previous history of trauma, fever, cough, hemoptysis, jaundice, or abdominal swelling, nor did he have any past history of malignancy, radiation, or long-term medication intake. All routine laboratory tests were normal.

Imaging assessment demonstrated an elevated right hemidiaphragm on chest X-ray [Figure 1], with a homogeneously opaque area occupying the right lower region, obscuring the cardio-phrenic angle and blunting the right costophrenic angle. No rib destruction or calcifications were observed. Contrast-enhanced CT showed a large, lobulated, heterogeneously enhancing soft tissue mass in the right hypochondriac region involving the subdiaphragmatic and supradiaphragmatic region, approximately measuring 14 cm × 11 cm × 14 cm in size. The right diaphragm was not separately visualized [Figure 2]. The supradiaphragmatic portion was seen abutting the right atrium, esophagus, intrathoracic inferior vena cava, and right inferior pulmonary vein. In the subdiaphragmatic portion, the mass encroached into the superior aspect of the right hepatic lobe (segments VII and VIII) with irregular thickening of the visualized diaphragmatic dome. In the arterial phase, the lesion was supplied by the right inferior phrenic artery which was branch of the abdominal aorta. Magnetic resonance imaging (MRI) confirmed a large, lobulated mass lesion showing heterogeneously hyperintense signal on T2 sequences with central necrosis centered on the right dome of the diaphragm [Figure 3].

Figure 1.

Chest radiograph (PA view) showing an elevated right hemidiaphragm with a well-defined right lower thoracic opacity obscuring the right cardio-phrenic and blunting of costophrenic angle

Figure 2.

Contrast-enhanced computed tomography demonstrating a large lobulated, heterogeneously enhancing soft-tissue mass centered on the right hemidiaphragm. Axial images (a-d) Shows extension into thoracic and abdominal compartments with compression of the intrahepatic and intrathoracic IVC and a few necrotic areas within. Coronal reformatted images (e-g) Shows transdiaphragmatic spread, with the supradiaphragmatic portion abutting the right atrium and the subdiaphragmatic portion infiltrating hepatic segments VII and VIII, causing irregular diaphragmatic thickening and mild perilesional fluid. Sagittal reformatted image (h) Shows continuity of supra- and subdiaphragmatic components centered on right dome of diaphragm. Maximum intensity projection image (i) Demonstrates arterial supply from the right inferior phrenic artery (white arrow)

Figure 3.

T2-weighted MRI images demonstrating a large lobulated mass of right diaphragmatic origin. (a) Coronal image: Shows transdiaphragmatic extension into thoracic and abdominal compartments. (b) Sagittal image: Depicts continuity of the lesion across the right hemidiaphragm with associated diaphragmatic thickening and minimal pleural effusion

Histopathological study of a core biopsy [Figure 4] showed a spindle-shaped malignant neoplasm in interlacing fascicles, showing marked nuclear atypia, prominent nucleoli with high mitotic count (20 per 10 high-power fields). Immunohistochemistry [Figure 5] showed intense positivity for myogenin and MyoD1, establishing the differentiation towards skeletal muscle, whereas the markers for epithelial, smooth muscle, neural, and other spindle cell sarcomas were negative. The patient was referred to onco-surgery for multidisciplinary assessment and further management.

Figure 4.

Histopathological study shows a spindle-shaped malignant neoplasm in interlacing fascicles, showing marked nuclear atypia, prominent nucleoli

Figure 5.

Immunohistochemistry shows intense positivity for myogenin and MyoD1 Magnification value (400x)

DISCUSSION

RMS is a malignant neoploasm of skeletal muscle precursors, which is most prevalent in children and adolescents. Of all the different histologic subtypes of RMS, spindle cell RMS is very rare.[7] Primary diaphragmatic RMS is a very rare tumor with only a few cases described in the literature. The diaphragm, as a muscle, is a possible site of origin for RMS; however, such tumors are rare.[8] Prior cases have been reported of pleomorphic RMS developing from the diaphragm, but spindle cell RMS in this area is exceedingly rare. The rarity of RMS of the diaphragm presents a critical challenge in terms of diagnosis because symptoms can be nonspecific and readily assigned to more frequent conditions, which can cause delays in diagnosis.[9]

The clinical presentation of diaphragmatic RMS can be variable, with patients presenting with nonspecific symptoms of chest pain, dyspnea, or abdominal pain. In the presented case, the patient had progressive shortness of breath with right-sided pleuritic chest pain over weeks. Imaging studies, i.e. chest radiograph and contrast-enhanced CT, showed a large, lobulated, heterogeneously enhancing mass centered on the right hemidiaphragm extending to both thoracic and abdominal spaces. The mass showed features of malignancy, such as necrosis and compression of surrounding structures, that made the diagnosis of spindle cell RMS.[10]

A histopathological study is important for diagnosing RMS. In our case, biopsy samples showed a spindle-shaped malignant tumor in interlacing fascicles with marked nuclear atypia, hyperchromatic nuclei, prominent nucleoli, and a high mitotic count. Immunohistochemistry showed intense positivity for myogenin and MyoD1, establishing skeletal muscle differentiation, and was negative for epithelial, smooth muscle, neural, and other spindle cell sarcoma markers.

Treatment of diaphragmatic RMS is typically multimodal and involves surgical resection, chemotherapy, and irradiation in certain cases. The type of surgical resection varies according to the size, location, and involvement of the surrounding structures. In the current case, the patient was referred to onco-surgery for further treatment, highlighting the importance of a multidisciplinary team in the handling of rare and complex tumors.

Prognosis in diaphragmatic RMS patients is variable and is based on several variables, such as histologic subtype, tumor size, tumor location, and success of resection. The prognosis of spindle cell RMS is overall better than other forms of RMS. The fact that diaphragmatic RMS is rare, along with the risk of recurrence or metastasis, underscores the need for close follow-up and personalized treatment regimens.

CONCLUSION

Adult diaphragmatic spindle cell rhabdomyosarcoma is a highly rare and malignant neoplasm that presents serious diagnostic and therapeutic challenges. A thorough CT and MRI assessment is essential to ascertain the extent of the tumor, its association with surrounding organs, and to map out surgery. Management depends on a multidisciplinary strategy, including total surgical resection, systemic chemotherapy, and selective radiation therapy when necessary. Prompt recognition and multidisciplinary care are of utmost importance in securing successful outcomes in this rare neoplasm.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.