Malignant peripheral nerve sheath tumour of the renal parenchyma presenting as a fast growing atypical renal cyst

Abstract

Malignant peripheral nerve sheath tumours (MPNST) of the kidney are very rare, with only 3 cases reported in the English and French literature. However, we report the first case of fast growing atypical renal cyst where a magnetic resonance imaging was an interesting adjunct to the computed tomography scan in imaging this rare tumour.

Fig. 1

(A) Contrast enhanced computed tomography (CT) scan shows a 8-cm left renal lesion with a density of 13 Hounsfield units and slight peripheral rim enhancement. (B) T₁-weighted magnetic resonance image reveals a slightly hypointense left renal lesion (C) which shows peripheral and heterogeneous internal enhancement following gadolinium administration. (D) On T₂-weighted image, the left renal lesion appears heterogeneously hyperintense, with a small and very hyperintense (cystic) posterior component. (E) There is a significant growth to 14 cm of the left renal lesion on a follow-up contrast enhanced CT scan done 3 months later. The lesion shows heterogeneous internal enhancement and displaces the kidney posteriorly.

Fig. 2

Gross pathology specimen removed by a transperitoneal laparoscopic approach. Ruler graduated in inches.

Fig. 3

(A) Microscopic imaging (hematoxylin and eosin stain; 40×) of the tumoural proliferation composed of spindle cells with moderate cellularity and nuclear atypia (B) Immunohistochemical study demonstrating strong S-100 immunoreactivity consistent with the diagnosis of malignant peripheral nerve sheath tumours. (C) 40% to 50% of the tumour cells were positive for Ki-67. Tumour cells were negative for muscle markers.