Hemangioma in the posterior mediastinum.

Sir,

Benign vascular tumors of the mediastinum are rare. Hemangiomas are estimated to constitute about 0.5% of all mediastinal tumors.[1] They originate from vascular endothelium and probably represent developmental malformations rather than true neoplasms.[2] Seventy five percent of the lesions appear before the age of 35 years, though it has been found between 2 months to 76 years of age. There is no gender preponderance. Sixty eight percent of the lesions are located in the anterior mediastinum but it can rarely occur in posterior mediastinum.[3] Middle mediastinal hemangiomas are mostly seen in contiguity. Total surgical removal is the preferred modality of treatment in most of the cases.[4]

A 56-year-old female referred to our out-patients department by a local physician had history of right-sided dull aching chest pain for last 6 months. There was no other local or systemic symptom. General physical examination was unremarkable. Examination of chest and abdomen was normal. Chest radiograph revealed a right paracardiac opacity [Figure 1]. Computed tomography (CT) scan of thorax revealed a 65 × 53 mm sized homogeneous mass lesion of soft tissue density (+60 HU) in right posterior mediastinum [Figure 2]. The outline of the lesion was fairly regular and there were foci of calcifications at the periphery of the lesion. No area of fat or fluid density was noted. Following intravenous contrast administration it showed homogenous enhancement (+86 HU) [Figure 3]. Fine needle aspiration cytolog y (FNAC) under CT guidance was noncontributory. She was referred to cardiothoracic surgeon for surgical intervention. A right posterolateral thoracotomy was done under general anesthesia and pleural space was entered via fifth intercostal space. Total excision of the mass was done. Histopathological examination of the resected specimen revealed a benign cavernous hemangioma [Figure 4]. Postoperative period was uneventful.

Figure 1

Chest radiograph (posteroanterior view) showing a right sided paracardiac mass lesion

Figure 2

CT scan of thorax showing a homogeneous mass lesion of soft tissue density in posterior mediastinum with peripheral foci of calcifications

Figure 3

Contrast-enhanced CT scan of thorax showing homogenous enhancement of the lesion

Figure 4

Microphotograph of histopathology of the resected mediastinal mass showing benign cavernous hemangioma (H&E stain, 40×)

A significant number of the patients with mediastinal hemangiomas are asymptomatic and detected incidentally in chest radiograph. Symptoms, if present, are secondary to infiltration to the adjacent structures. Anterior mediastinal hemangioma may present as fullness and mass in the neck. Other symptoms include nonspecific chest pain, shortness of breath, or hemoptysis. Invasion of local structures may result in Horner's syndrome, dysphagia, or superior vena caval syndrome.[5] Mediastinal hemangioma may be associated with Osler–Weber–Rendu Syndrome or peripheral hemangiomas of skin, spleen, liver, and kidney.[67] Chest radiograph usually reveals the lesion as rounded or lobulated mass with smooth margin. Phleboliths are seen in 10% cases and CT scan is more sensitive to detect these lesions.[8] CT scan reveals the extent of the tumors and invasion of the adjacent structures. Noncontrast CT scan thorax usually reveals heterogeneous mass with well-defined smooth or lobulated margin but it does not have a true capsule. It can rarely be homogeneous. It shows any of the four types of enhancement after intravenous contrast such as minimal heterogeneous (most common), classical peripheral or central puddling of contrast (common in hepatic hemangioma), homogenous enhancement, and nonenhancement.[9] Nonspecific punctate calcification may be seen which is also seen in teratoma or cartilaginous tumors.

In the bone window, ring-like calcifications with central-lucency-called phleboliths can be seen which are virtually diagnostic for hemangioma.[10] Gradually increasing and persistent enhancement may be seen on dynamic contrast-enhanced CT scan. Delayed images may reveal large draining vein.[9] Low density areas representing fat may be seen in CT scan. MRI of these tumors is often hypointense on T1W1 with few high signal foci due to methemoglobin formation or fat.[10] They are hyperintense on T2W1. CT scan of thorax in our patient revealed a homogenous mass with flecks of calcification and homogenous enhancement without any phleolith or fat density.

Sometimes mediastinal hemangiomas encase mediastinal structures and it may appear difficult to differentiate it from malignant lesion in CT and MRI of thorax. Hence, histopathological confirmation is mandatory. Mediastinoscopic or bronchoscopic biopsy is contraindicated because of the risk of hemorrhage.[11] On gross examination, it appears as soft encapsulated red–brown mass of size between 1 and 16 cm being spongy on cut section. Occasionally, it may extend to adjacent tissue. Microscopically, it appears as thick-walled interconnecting vascular spaces lined by flattened cuboidal epithelium along with a varying amount of interspersed stromal elements like fat, myxoid, and fibrous tissue. According to the size of vascular spaces, it can be of four varieties such as cavernous (most common), capillary, venous, and mixed.[11]

Surgery rather than percutaneous biopsy is recommended for diagnosis and treatment. CT scan demonstrates aberrant draining vessel that is vital for surgical planning. Well-circumscribed lesions are suitable for total excision and infiltrative tumors are generally managed with subtotal excision that also produces acceptable results.[11] Residual masses generally do not grow. Perioperative hemorrhage is not a major issue in an expert hand. Malignant degeneration does not occur in mediastinal hemangioma, as also continued local invasion or aggressive recurrence.[11] However, cyst formation, fibrosis, and ossification are seen in few cases. Radiotherapy is not useful as a primary mode of treatment.

Common differential diagnosis of a tumor of posterior mediastinum includes neurogenic tumor, mediastinal lymphoma, and lymphangioma.[8] Intact intervertebral foramina and the absence of neurodeficit or local invasion of ribs or vertebral body go against the diagnosis of neurogenic tumor. Mediastinal lymphoma generally appears as heterogeneous mass, and calcification in untreated mediastinal lymphoma is extremely rare. Lymphangiomas are cystic lesions that classically do not enhance after contrast administration. Calcification is also unusual

Our case of mediastinal hemangioma has several atypical features that deserve mention. They include atypical location, presentation in adult age, homogenecity in CT scan, and the absence of phlebolith. The recognition of the possibility of hemangioma even when the patient presents with atypical features will direct us to opt for open surgical resection and avoid potentially hazardous percutaneous image guided biopsy.