EDUCATIONAL CASE REPORT Fine needle aspiration cytology of cystic partially differentiated nephroblastoma of the kidney A. Nayak*, V. K. Iyer*, S. Agarwala   and K. Verma* Departments of *Pathology and   Paediatric Surgery, AIIMS, New Delhi, India Accepted for publication 10 September 2004 Keywords: cystic partially differentiated nephroblastoma, Wilms tumour, fine needle aspiration cytology Introduction Cystic partially differentiated nephroblastoma (CPDN) is an uncommon renal tumour of infancy. It needs to be differentiated from other cystic renal tumours such as cystic nephroma (CN) and cystic Wilms tumour (CWT). This distinction has practical importance in view of differences in therapy and prognosis. Since the first description of CPDN 1 many reports describing its histological features have appeared in the literature; 2–4 however, features of CPDN on fine needle aspiration cytology (FNAC) smears are not well described, with only a single case report. 5 We present a case of CPDN, which serves to highlight the cytological features of CPDN, and discuss the differential diagnostic consid- erations on FNAC. Case report A seven-and-half-month-old boy presented with a history of a right abdominal lump of over 1 month’s duration. The patient was otherwise asymptomatic. Ultrasonography of the abdomen revealed a large 11 · 9 cm multicystic mass in the right kidney. No solid areas were identified within the mass. Computer- ized tomography (CT) scan confirmed these findings. Fine needle aspiration of the mass was performed as an outpatient procedure using a 23-gauge needle and a 10-ml syringe fitted onto a syringe holder. Two millilitres of fluid was aspirated from the mass, from which cytospin slides were prepared and stained by Papanicolaou and May-Gru ¨ nwald–Giemsa stains. Cytological features Cytospin preparations from the aspirated fluid showed scant to moderate cellularity. Two types of cells were identified. Epithelial cells were seen in small groups. These cells had moderate cytoplasm and vesicular nuclei with nucleoli, focal moderate pleomorphism and hyperchromasia (Figures 1 b and 2 b ). Similar cells were also seen singly, along with cells resembling cyst macrophages. The other cell type consisted of loose clusters of a few small round cells with scant cytoplasm and hyperchromatic nuclei (Figures 1 a and 2 a ). In contrast to the epithelial cell groups, the second cell type was discohesive with irregular borders and a few single cells. The cells were smaller with scant cytoplasm and had a smaller but markedly hyperchromatic nucleus. These cells, better seen on Papanicolaou than May-Gru ¨ nwald–Giemsa-stained smears, were interpreted as blastemal cells and a diagnosis of either CPDN or CWT was given. Subse- quently a complete nephrectomy was performed, followed by routine histopathological examination. Histopathological features The right nephro-ureterectomy specimen measured 11 · 9 · 8.5 cm and weighed 390 g. On cut section, many unilocular and multilocular cysts varying in size from 0.2 to 0.4 cm were identified. The walls of the cysts were thin, and serous fluid was seen within the cavities. No solid area or areas of necrosis and haemorrhage were noted. A small portion of normal kidney parenchyma measuring 3 · 1.5 cm was iden- tified near the hilum. On microscopic examination, the tumour showed multiple cysts lined mostly by flattened to cuboidal epithelium (Figure 3a). However in focal areas, the cells lining the cysts showed nuclear enlargement, hyperchromasia and pleomorphism (Figure 3b). Correspondence: Dr Venkateswaran K. Iyer, Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi- 110 029, India. Tel.: +91 11 2658 8700 (ext. 4393); Fax: +91 11 2658 8663; E-mail: iyer_venkat2@rediffmail.com Cytopathology 2006, 17, 145–148 ª 2006 Blackwell Publishing Ltd 145