A case of mediastinal mesenchymal tumor with pericytic neoplasm feature that responded to radiation therapy

Abstract

Here, we report a case of mediastinal mesenchymal tumor with a pericytic neoplasm feature that responded to radiation therapy. A 43‐year‐old man visited our hospital with a complaint of esophageal obstruction and chest pain. Chest computed tomography revealed a middle mediastinal tumor and a mesenchymal tumor was diagnosed with a pericytic neoplasm feature by video‐assisted thoracoscopic biopsy. The definitive treatment for soft tissue tumor is surgical resection; however, the mediastinal tumor was unresectable because of esophageal and tracheal invasion. Radiation therapy was administered and there was a partial tumor response and 2 years disease‐free status. With a review of the literature, we discuss the clinical and pathological characteristics of this rare tumor and its treatment.

We experienced a case of mediastinal mesenchymal tumor harboring a pericytic neoplasm feature. This tumor invaded the esophagus and trachea, and we considered it unresectable. We administered radiation therapy, and the patient had good tumor shrinkage, symptom relief, and long progression‐free survival.

INTRODUCTION

In the mediastinum, mesenchymal tumor is rare, whereas thymic tumor, cystic disease, and neurogenic tumor are common. A pericytic neoplasm is a mesenchymal tumor that exhibits differentiation towards myoid/contractile perivascular cells. It is divided into three subcategories consisting of glomus tumor, myopericytoma, and angioleiomyoma. ¹ Surgical resection is recommended as the definitive treatment of soft tissue tumor, but some cases are unresectable depending on the site of origin. Here, we describe a case of unresectable mediastinal mesenchymal tumor with a pericytic neoplasm feature that responded to radiation therapy.

CASE REPORT

A 43‐year‐old male visited our hospital with a complaint of esophageal obstruction and chest pain. Chest X‐ray and enhanced computed tomography (CT) detected a well‐enhanced tumor of 50 mm in the middle mediastinum (Figure 1a,b). 18F‐fluorodeoxyglucose positron emission tomography (FDG‐PET) showed a localized hyperaccumulation of SUVmax 12.4 (Figure 1c). Esophagogastroduodenoscopy revealed a submucosal elevation and a lobulated mass in the middle esophagus (Figure 2a). Bronchoscopy showed redness and irregular longitudinal folds of the tracheal membranous portion, which suggested tracheal invasion of mediastinal tumor (Figure 2b).

FIGURE 1.

Imaging tests before treatment. (a) Chest X‐ray shows enlargement of the mediastinum. (b) Enhanced chest computed tomography (CT) reveals a well‐enhanced tumor of 50 mm in the middle mediastinum. (c) 18F‐fluorodeoxyglucose positron emission tomography (FDG‐PET) shows localized hyperaccumulation of SUVmax 12.4 in the mediastinal tumor.

FIGURE 2.

Endoscopic findings. (a) Esophagogastroduodenoscopy reveals a submucosal elevation and a lobulated mass in the middle esophagus. (b) Bronchoscopy shows redness and irregular longitudinal folds of the tracheal membranous portion, which suggest bronchial invasion of mediastinal tumor. (c–e) Using three‐dimensional computed tomographic, we planned radiation therapy for the mediastinal tumor.

A sufficient sample for histological diagnosis was not obtained following transesophageal ultrasound‐guided fine needle aspiration biopsy; thus, we performed video‐assisted thoracoscopic biopsy. The specimen showed small round cells with aggregation of nuclear chromatin with fission image but no necrotic background. The cells resembled glomus cells as they had a cuboidal or polygonal shape, clearly demarcated from the surrounding area; eosinophilic cytoplasm; and a round nucleus in the center that proliferated around the vascular lumen. Immunohistochemical staining was positive for α‐smooth muscle actin (SMA) and CD146, and negative for type desmin, IV collagen, cytokeratin, S‐100, CD34, calponin, and myogenin (Figure 3). MIB‐1 labeling index was 9.2%. We diagnosed mesenchymal tumor harboring a pericytic neoplasm feature (Figure 3).

FIGURE 3.

Pathological findings of the video‐assisted thoracoscopic biopsy specimen. (a) Hematoxylin–eosin (HE) staining ×20. (b) HE staining ×40. (c) Immunohistochemical staining (IHC) for α‐smooth muscle actin (SMA) is positive. (d) IHC for CD‐146 is positive. (e) IHC for desmin is negative. (f) IHC for collagen IV is negative.

We considered this tumor unresectable because of esophageal and tracheal invasion. We evaluated actual dose distribution and administered thoracic radiation therapy (60 Gy in 30 fractions). (Figure 2c–e). After radiation therapy, his esophageal obstruction and chest pain improved, and chest CT and esophagogastroduodenoscopy showed regression of the mediastinal tumor (Figure 4). There was no evidence of recurrence or metastasis after 2 years from radiation therapy.

FIGURE 4.

Chest X‐ray, enhanced CT, and esophagogastroduodenoscopy findings before radiation therapy (a–c) and 2 years after radiation therapy (d–f). Radiation therapy shrank the mediastinal tumor and esophageal invasion.

DISCUSSION

Here, we report a rare case of mediastinal mesenchymal tumor with a pericytic neoplasm feature. Mesenchymal tumors arising in the mediastinum are rare, and the estimated incidence is 2%–6% of mediastinal neoplasms. Among them, pericytic neoplasms are rare, although lipomatous tumors, solitary fibrous tumor (SFT), and inflammatory myofibroblastic tumor (IMT) are sometimes observed. ² , ³ Pericytic neoplasms are classified into three subtypes of glomus tumor: malignant glomus tumor, myopericytoma, and angioleiomyoma. ¹ These tumors usually occur in the subcutaneous region of distal extremities. Few cases of mediastinal pericytic neoplasms have been reported and mediastinal glomus tumors have been reported to be the most common tumor type among them. ³ , ⁴ , ⁵ , ⁶ , ⁷ In addition, most pericytic neoplasms, such as glomus tumor, are localized and resectable; however, in the present case, the tumor atypically invaded the esophagus and bronchus.

We diagnosed this tumor as a mesenchymal tumor with pericytic neoplasm features. The well enhanced mass on CT of this case was compatible with that of pericytic neoplasms represented by glomus tumor. ⁶ , ⁸ This mediastinal tumor showed hyperaccumulation on FDG‐PET. There have been few previous reports of FDG‐PET findings of pericytic neoplasms ⁹ and no consensus has been developed. Biopsy specimen showed small round cell tumors, and the immunohistological characteristics, such as being positive for α‐SMA and CD146 and negative for cytokeratin, S‐100 protein, and desmin, suggested pericytic neoplasm. We could not diagnose this mesenchymal tumor as glomus tumor because type IV collagen was negative. ¹

After radiation therapy, the patient had good tumor shrinkage, symptom relief, and long progression‐free survival. The definitive treatment of localized soft tissue tumor is complete surgical resection, as even in cases where benign glomus tumor remains, the tumor may recur, ¹⁰ or malignant glomus tumor may arise from the same region. ¹¹ In the present case, we found redness and irregular longitudinal folds of the tracheal membranous portion on endobronchial examination exceeding 3 cm, and the findings implied invasion of tracheal membrane by tumor. We decided that even if we resected this tumor by surgery, reconstructive surgery would be difficult. Thus, radiation therapy was administered to the mediastinal mesenchymal tumor harboring pericytic neoplasm, as radiation therapy is often performed to unresectable glomus tumors located in the temporal bone or skull base. ¹² We considered complete resection of the residual tumor after radiotherapy, but surgical resection after radiotherapy could be difficult because tissue scarring might occur due to inflammation caused by irradiation. ¹³ We considered the occurring risk of postoperative complication would be high, and we also thought that there was little evidence for surgical treatment to perform after radiation. We will continue to follow up this patient to confirm whether complete remission by radiation therapy occurs.

In conclusion, we report a case of mediastinal mesenchymal tumor harboring a pericytic neoplasm feature. Radiation therapy may be useful for unresectable cases of such mesenchymal tumors.

AUTHOR CONTRIBUTIONS

Dr. Muramaoto was in charge of diagnosing and treating this patient, and Dr. Kanda and Kozumi assisted Dr. Muramaoto in diagnosing and treating him. Dr. Kobayashi and Dr. Koizumi provided diagnostic advice to Dr. Muramoto, and they also treated this patient with Dr. Muramoto. Dr. Tamada helped Dr. Muramoto in diagnosis of this patient. Dr. Koiwai and Fukazawa helped Dr. Muramoto in treating this patient. Dr. Tamada and Koiwai gave advice Dr. Muramoto in the section of discussion.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflict of interest.

Muramoto M, Kanda S, Kobayashi T, Tamada H, Fukazawa A, Koiwai K, et al. A case of mediastinal mesenchymal tumor with pericytic neoplasm feature that responded to radiation therapy. Thorac Cancer. 2023;14(13):1204–1207. 10.1111/1759-7714.14855