Massive renal angiomyolipomas and other manifestations of tuberous sclerosis

Clinical History

A 38-year-old female patient who was diagnosed with tuberous sclerosis 17 years ago, with no pain, renal insufficiency or other clinical manifestations.
A thoracoabdominal CT was performed in her reference hospital leading to the radiological diagnosis of renal carcinoma.
She came to our hospital looking for a second opinion.

Imaging Findings

Figure 1. Thoracic CT:
a, b: Multifocal micronodular pneumocyte hyperplasia: small nodules, distributed randomly across the pulmonary parenchyma.

Figure 2. Abdominal CT:
a, b, c, d, e: Angiomyolipomas: non-calcified renal masses with fat density.
e & f: Note the enhanced solid mass in the renal left upper pole. Because of vascular component of angyomiolipomas differential diagnosis with RCC may be difficult.

Figure 3. Brain MR:
a, b, c, d: Subependymal nodules: calcified in 90% of cases. On MRI they appear as hyperintense lesions on T1WI and hypointense on T2WI. An intense gadolinium enhancement is typically present in this lesions.
e, f, g: Calcified subependymal nodule in Monro’s foramen.
h: White matter radial bands: hyperintense bands on T2WI or FLAIR and hypointense on T1WI, ranging from the periventricular white matter to the cerebral cortex or characteristically to cortical tubers.
i: Cortical tubers: low signal intensity on T1WI and high signal on T2WI and FLAIR.

Discussion

Tuberous sclerosis (TS) is a systemic disease characterized by the appearance of hamartomas in multiple organs [1-4].

It is a congenital autosomal dominant disease caused by mutation of TSC1 or TSC2 genes [1-4].

Definitive diagnosis of TS have to meet two major criteria or one major and two minor based on typical manifestations of the disease and may involve several organs [1-4].

Our patient had cutaneous hamartomas and radiological manifestations characterizable as cerebral tubers, subependymal nodules (SEN), radial bands, multifocal micronodular pneumocyte hyperplasia (MMPH) in pulmonary parenchyma and renal angiomyolipoma. Below we will review these conditions:

Neurologically, cortical tubers and SEN can be observed in up to 95% of patients [2, 3, 5].
Cortical tubers are epileptogenic hamartomas, which has lost the normal architecture of the cerebral cortex [1-3]. They calcify in 50% of cases and thus can be diagnosed on CT [3]. However, the technique of choice is MRI, where they appear as lesions with low signal intensity on T1WI and high signal on T2WI and FLAIR, this pattern is reversed in the case of children under 1 year due to poor myelination of brain [2, 3].
SEN are hamartomatous lesions in the lateral wall of the ventricles that calcify in 90% of cases [1-3].

On MRI appear as hyperintense lesions on T1WI and hypointense on T2WI [2]. Note the calcified ependymoma in the foramen of Monro in our patient, which is the typical location of giant cell astrocytoma, however, calcification makes atrocytoma degeneration unlikely.

Another feature of the TS is the involvement of white matter radial bands secondary to altered migration of glial cells during embryogenesis [2, 3, 5]. It is present in 80% of patients with TS [3]. Usually it manifests as hyperintense bands on T2WI or FLAIR and hypointense on T1WI, ranging from the periventricular white matter to the cerebral cortex or characteristically to a cortical tubers.
Our patient had MMPH, a rare condition that involves hyperplasia of type II pneumocytes. It is more common in women and manifests as small nodules, distributed randomly across the pulmonary parenchyma [2].

Both kidneys had massive angiomyolipomas, which are benign tumours consisting of fat, vascular and smooth muscle cells [1-3]. On CT they are identified as non-calcified renal masses with fat density. Because of its vascular component, some low-fat angiomyolipoma can enhance after administration of intravenous contrast, which hinders the differential diagnosis vs renal cell carcinoma [2, 3] like in our patient, in whom kidney biopsy was performed for a definitive diagnosis.

In conclusion, tuberous sclerosis is a disease that can affect multiple organs in which radiology represents a cornerstone for diagnosis.

Differential Diagnosis List

Final Diagnosis

US-guided biopsy proved renal angyomiolipoma in the context of TS.

URL:	https://www.eurorad.org/case/12296
DOI:	10.1594/EURORAD/CASE.12296
ISSN:	1563-4086