CT findings of malignant pulmonary metastasis in von Recklinghausen's disease

Clinical History

A 62-year-old male presented with von Recklinghausen's disease, who had been operated twice on a left axillary lesion and for pulmonary metastases.

Imaging Findings

A 62-year-old male patient presented with von Recklinghausen's disease. This patient was followed up for an important dysfunction of his pulmonary parameters that correlated with his disease. The patient had been operated twice on a left axillary lesion and for pulmonary metastases.The follow-up CT exams showed that there was a relapse of the left axillary lesion (Fig. 1) and the presence of a lesion in the right pulmonary hilum (3.5 x 3.6 cm in size) that compressed the main right bronchus and the right pulmonary vein (Fig. 2). Another lesion at the upper right costal pleura involving the fissure was clearly visible (Figs. 3, 4). A subcutaneous lesion was detected in the posterior thoracic wall, under the scapula on the right side (Fig. 5). CT scans demonstrated the presence of solid fusiform masses with often seen central areas of a low attenuation for the presence of lipid foci of schwann cells, cystic degenerations. The masses were usually well defined with attenuation values of 30–40 Hounsfield Unit (HU) (6,7). According to the National Institutes of Health (NIH), two types of neurofibromatosis are known to be defined: neurofibromatosis type 1 (NF1) also referred to as von Recklinghausen's disease and neurofibromatosis type 2 (NF2) or bilateral eighth nerve schwannomas syndrome (1–3). NF1 is an autosomal dominant disorder with an almost 100% penetrance but a variable expression and with an incidence of one case per 3000–4000 people. The alternate gene locus is on the long arm of Chromosome 17, and it encodes for a protein named neurofibromin which acts as a tumour-suppressor oncogene (1).

Discussion

Neurofibromatosis includes a group of heterogeneous conditions. In most individuals, the cutaneous findings are prominent and include café-au-lait spots (CAL), neurofibromas, and axillary or inguinal freckling (70% of the cases). Lisch nodules are iris melanotic hamartomas which are found in almost all adult patients on doing a slit-lamp examination (1). The diagnoses of NF1 are made if two or more of the following signs are found: the presence of six or more CAL larger than 5 mm dimensions in prepubertal children and larger than a size of 1.5 cm in postpubertal individuals; two or more neurofibromas of any type or one plexiform neurofibroma; multiple freckles in the axillary or inguinal region; a distinctive osseous lesion, such as sphenoid dysplasia or thinning of the long bone cortex, with or without pseudoarthrosis; optic glioma; two or more iris hamartomas (Lisch nodules) seen on performing a slitlamp or biomicroscopy examination; a first-degree relative with NF1. Neurofibromas arise within or are attached to nerve trunks anywhere in the skin, in the body, and in the intracranial and intraspinal spaces. Histologically, neurofibromas comprise fibroblasts, Schwann cells that are predominant, and neurites. Multisystemic alterations are common, such as seizures and intellectual compromise, optic and acoustic involvement, intracranial and spinal tumours, an increased incidence of malignancies, congenital osseous defects, endocrine disorders, gastro-intestinal tract involvement, and vascular anomalies. The tumours are usually found to be benign but in about 3% of the patients, nodular and plexiform neurofibromas transform to malignant peripheral nerve-sheath tumours (1,2,6,7). An X-ray scan was taken, which depicted the evident skull abnormalities, multiple frontobasal and osteoarticular defects and other bone deformities. A sonography when taken demonstrated that neurofibromas are mostly hyperechoic with coarse internal echoes and lobulated margins. Nonplexiform neurofibromas in NF1 appear as hypoechoic fusiform masses with relatively regular and well-defined margins. CT scans demonstrate these solid fusiform masses in the distribution of nerves, with central areas of a low attenuation for the presence of lipid foci of schwann cells, cystic degenerations.The masses usually have values of 30–40 HU. Plexiform neurofibromas are depicted as widespread sheets of nodular tissue with attenuation values identical to the fusiform form. Paraspinal neurofibromas may be seen at every level, with various sizes. On magnetic resonance imaging, we can observe intracranial neural sheath tumours as being isointense to brain tissue on T1-images and hyperintense to brain tissue on T2-images. After the administration of a contrast agent it is found that tumours enhance intensely. Both schwannomas and neurofibromas are hypointense or mildly hypointense compared to the spinal cord as seen on T1-images and heterogeneously hyperintense as seen on T2-images (6,7). The NF1 is a complex multisystemic disorder, and some alterations can coexist together. These tumours can represent a several pathological conditions such as abdominal aortic aneurysms, brain astrocytomas, artero-venous malformations idiopathic pulmonary fibrosis, neuroblastomas, parathyroid-adenomas, thyroid nodules, lymphomas, lymphangiomatosis, metastasis of an unknown primary tumour or lung tumour, etc. Paravertebral neurofibromas can extend into the spinal canal and mimic ganglioneuromas or cystic-formations (caused by myxoid degeneration). A contrast agent is sometimes useful, but neurofibromatosis has the same features of a neoplasm. In all cases, it is fundamental to obtain the clinical aspects and the pathological history of the patient and the clinical correlations and symptoms of the diseases mentioned above. When there are still doubts and the imaging features do not give a sure and clear diagnosis, the biopsy of these lesions can demonstrate the nature of the lesion and propose a definitive diagnosis (6,7). In the case that we describe, there is relapse of the lesion after surgical exeresis (which proved it to be a malignant schwannoma) and also that there is an unusual association with pulmonary metastases (4,5).

Differential Diagnosis List

Final Diagnosis

Relapse after exeresis (malignant schwannoma).

URL:	https://www.eurorad.org/case/2838
DOI:	10.1594/EURORAD/CASE.2838
ISSN:	1563-4086