Coexistence of Primary Hepatic Myopericytoma and Mediastinal Castleman Disease in One Patient: An Interesting 18F-FDG PET/CT Imaging Case
Primary hepatic myopericytoma (MPC) is an exceedingly rare soft tissue tumor, first conceptualized by Dictor in 1992. The term “myopericytoma” was later adopted by Granter in 1998 to describe this specific type of tumor. While MPCs predominantly arise in the skin and superficial soft tissues of the distal extremities, their occurrence in the liver is exceptionally rare. Surgical resection of MPCs generally yields a favorable prognosis, although there have been occasional reports of recurrence or metastasis. Castleman disease (CD), first described in 1954, is a lymphoproliferative disorder that most commonly affects the chest but can also manifest in other regions such as the pelvis, neck, retroperitoneum, and muscles. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has proven to be an effective diagnostic tool for both MPC and CD. This case report presents a rare instance of the coexistence of primary hepatic MPC and mediastinal CD in a single patient, as revealed by 18F-FDG PET/CT imaging.
The patient, a 56-year-old female, was admitted to the hospital following the identification of a hepatic lesion during an abdominal ultrasound. Initial serum tests for alpha-fetoprotein, carcinoembryonic antigen, and carbohydrate antigen 19-9 returned negative results. To further elucidate the nature and extent of the lesion, the patient underwent 18F-FDG PET/CT imaging. The PET/CT scan revealed two distinct lesions: one in the left lobe of the liver and another in the mediastinum.
The hepatic lesion measured approximately 6.2 cm by 5.4 cm and exhibited a maximum standardized uptake value (SUVmax) of 3.9. The mediastinal lesion, on the other hand, measured about 4.9 cm by 3.7 cm and had a significantly higher SUVmax of 6.4. This discrepancy in metabolic activity suggested that the two lesions were of different etiologies. A biopsy of the mediastinal lesion was performed, and histopathological analysis confirmed the diagnosis of CD. Subsequently, the patient underwent a left hemihepatectomy, and the histopathological examination of the hepatic lesion confirmed the diagnosis of MPC. Immunohistochemical analysis of the hepatic lesion was positive for vimentin, CD34, smooth muscle actin (SMA), and showed a low proliferation index with Ki-67. Additionally, low-density lesions in the liver without tracer uptake were identified as cysts.
The incidental discovery of the mediastinal lesion during the 18F-FDG PET/CT scan was pivotal in the patient’s diagnostic and therapeutic journey. The distinct metabolic profiles of the hepatic and mediastinal lesions indicated the presence of two primary tumors rather than a single malignant tumor with metastatic spread. This information was crucial for guiding the patient’s treatment strategy, allowing for targeted interventions for each tumor.
The hepatic MPC, given its rarity, posed a diagnostic challenge. The imaging characteristics and histopathological findings were consistent with previously reported cases of MPC, which typically exhibit a benign clinical course but can occasionally recur or metastasize. The mediastinal CD, although more common, was an unexpected finding in this case. The higher SUVmax of the mediastinal lesion compared to the hepatic lesion underscored the utility of 18F-FDG PET/CT in differentiating between various types of tumors based on their metabolic activity.
The management of this patient highlights the importance of a comprehensive diagnostic approach, particularly in cases involving rare and co-occurring neoplasms. The use of 18F-FDG PET/CT not only facilitated the accurate localization and characterization of the lesions but also provided valuable prognostic information. The final diagnoses of MPC and CD were confirmed through histopathological examination, emphasizing the indispensable role of tissue biopsy in the diagnostic process.
In conclusion, this case report illustrates the rare coexistence of primary hepatic MPC and mediastinal CD in a single patient, as identified through 18F-FDG PET/CT imaging. The distinct metabolic profiles of the two lesions were instrumental in guiding the diagnostic and therapeutic approach. This case underscores the utility of 18F-FDG PET/CT in the evaluation of complex and co-occurring neoplasms, as well as the critical role of histopathological examination in confirming diagnoses. The successful management of this patient highlights the importance of a multidisciplinary approach in the diagnosis and treatment of rare and complex medical conditions.
doi.org/10.1097/CM9.0000000000001626
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