Ancient neurilemmoma

Case contributed by Prof Oliver Hennessy

Presentation

Incidental finding

Patient Data

Age: 54
Gender: Female
X-ray

Left paravertebral  based left upper zone mass located posteromedially with erosion of the inferior aspect of the posterior 4th rib. Lungs and pleural spaces are otherwise clear. Elevated left hemidiaphragm. Cardiomediastinal contour is within normal limits.

 

CT

There is a 37 x 65mm heterogeneous, partially calcified pleurally based mass in the left hemithorax abutting the proximal descending aorta. The mass partially erodes the posterior forth and fifth ribs and there is periosteal reaction on the anterosuperior edge of the forth rib. The mass is closely related to the intervertebral foramen of T4 and T5 however it is not widened.

Subpleural ground glass opacity in the lingular segment of the left upper lobe is of uncertain significance. Mild dependent right sided atelectasis.

Prominent mediastinal lymph nodes without lymphadenopathy by size criteria.

MRI

A large, lobulated 4.4 X 7.9 (axial) X 4.8 (cc) cm T1 hypointense, heterogenously T2 hyperintense, enhancing, pleurally based left paraspinal mass posteromedially is demonstrated at the level of T4 and T5. There are areas of non-enhancement/cystic change within the mass, likely representing necrosis. Foci of susceptibility change within the mass are in keeping with calcification seen on CT. The mass abuts but doesn't involve of the left T4/5 intervertebral foramen.

No overt rib destruction.

There is minor pressure erosion (saucerisation) of the adjacent ribs and thoracic vertebra.

This is not of pulmonary origin.

A focal right paracentral T5/6 disc extrusion is present, which causes anterior indentation/effacement of the thecal sac. A smaller left paracentral left T6/7 disc protrusion also causes minor thecal sac indentation.

No other significant spinal canal, lateral recess or foraminal stenosis.Marrow signal is normal. Vertebral alignment is unremarkable. No epidural mass or collection.Imaged lungs and other paraspinal structures are unremarkable, other than for dependent pulmonary atelectatic change.

Conclusion

Left T4/5 level pleurally-based mass as described, indeterminate.

This is a long-standing lesion causing pressure remodelling of the adjacent vertebrae and ribs without invasion, remaining entirely extra-osseous.

A solitary fibrous tumour is suspected.

A chondral lesion or neural lesion are thought less likely.

 

MACROSCOPIC DESCRIPTION: "Left posterior mediastinal mass":

Piece of tissue, 50g, 60x45x40mm with one surface covered by a shiny fibrous membrane and other surface roughened (inked blue). Sectioning reveals a multilobulated well circumscribed tumour with heterogenous areas of solid growth, haemorrhage, friable necrosis and calcification. The tumour abuts the inked margin.

 MICROSCOPIC DESCRIPTION: Sections show a well-circumscribed, partly encapsulated, paucicellular tumour containing thick walled hyalinised vessels, areas of haemorrhage and dystrophic calcification. Tumour cells show mild nuclear atypia with focal Verocay body formation. Tumour cells stain S-100 positive, whilst they are negative for Neu-N, NFP and CD34. Histological and immunohistochemical features are those of an ancient schwannoma.

DIAGNOSIS: Left posterior mediastinal mass - Schwannoma, with ancient features.

Case Discussion

Ancient neurilemmoma is a cellular form of ordinary neurilemmoma, showing nuclear polymorphism and hyperchromasia. The majority of these  lesions are benign.

Imaging features:

On plain CXR a paravertebral soft tissue mass is seen. There is often erosion of the adjacent rib and vertebral body, splaying of ribs may also be see.

Calcification in benign schwannomas is rare, it is seen with greater frequency in ancient neurilemmoma. If there is rib or vertebral destruction the lesion should be considered malignant.

CT is useful in defining the exact location of the mass and will better demonstrate adjacent bone involvement.Contrast enhancement will vary depending on tumour size and degree of necrosis

MR with contrast:

This is the preferred imaging modality. Multiplanar capabilities and soft tissue resolution will assist in evaluating the tumour, assessing craniocaudal extent and any extension into the spinal canal.

In large lesions enhancement will be heterogenous reflecting cystic degeneration and necrosis, homogenous enhancement is usual in small  lesions.

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Case information

rID: 33460
Case created: 13th Jan 2015
Last edited: 25th Dec 2015
System: Chest
Inclusion in quiz mode: Included

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