Dermoid cyst associated with segmental multicystic renal dysplasia: A rare case

Abstract

Most multicystic dysplastic kidneys (MCDKs) are detected prenatally, yet there is no clear consensus on initial evaluation and follow-up. We report the case of a 4-year-old male diagnosed with right pyelocalyceal dilation in utero, confirmed postnatally as MCDK. Follow-up ultrasounds revealed rapid growth of three upper pole cysts, reaching 8 cm. A right upper pole nephrectomy was performed, and histopathology revealed a renal dermoid cyst within segmental multicystic renal dysplasia. This case highlights the critical role of postnatal imaging and follow-up in detecting atypical features, including rare entities like intrarenal teratomas, enabling timely surgical intervention and improved outcomes.

1 Introduction

A dermoid cyst is classified as a type of well-differentiated mature cystic teratoma and it is commonly found in the midline of the body, close to the embryonic fusion line. It is rarely observed in the kidneys, and only a limited number of cases have been documented in the literature. We report a case of dermoid cyst associated with renal dysplasia in a 4-year-old male child, with a review of literature.

2 Case report

A 4-year-old male child, diagnosed prenatally with right pyelocalyceal dilation, was confirmed to have multiple hyperechoic microcysts in the upper right caliceal group after birth. Regular consultations showed no physical abnormalities, though follow-up ultrasounds indicated progressive enlargement of three upper polar cysts.

At birth, a renal ultrasound revealed moderate dilation of the superior calyceal system and multiple hyperechoic microcysts in the upper right kidney. The left kidney showed mild dilation of the pyelocalyceal cavities (7 mm anteroposterior diameter).

At 2 months, the child developed a febrile urinary tract infection (UTI). Ultrasound showed the right kidney measuring 58 mm, with a cystic lesion of 24 mm and a hyperechoic formation (18 × 8 mm), which was mobile. The left kidney measured 54 mm, with moderate global calyceal dilation (10 mm anteroposterior diameter). A voiding cystourethrography (VCUG) at 5 months confirmed bilateral vesicoureteral reflux (VUR), grade 2. DMSA renal scintigraphy showed symmetrical renal function with no scarring. Prophylactic urinary antiseptic treatment was started with regular clinical and radiological monitoring.

By 7 months, an uro-CT scan identified simple cortical cysts, the largest being 37 mm, and revealed finely delineated bilateral ureteropyelocaliceal cavities. At 11 months, the right kidney measured 75 mm, with three cysts (39 × 29 × 25 mm, 17 × 14 × 11 mm, and 10 × 6 × 5 mm). The left kidney remained normal, and no UTIs recurred, allowing discontinuation of prophylactic antibiotics at 1.5 years.

At 2 years, the right kidney measured 100 mm, with two upper polar cysts (60 × 50 × 53 mm and 15 × 12 × 2 mm). The left kidney remained normal. At 3.5 years, a follow-up ultrasound showed an exophytic upper polar cyst measuring 70 × 47 mm, with thin walls and incomplete septations. The left kidney continued to appear normal.

A CT-guided percutaneous cyst aspiration yielded serous fluid ( Fig. 1 ). Cytological analysis confirmed a paucicellular fluid devoid of anaplastic features. However, post-aspiration ultrasound revealed a cyst in the right kidney’s upper polar sinus (81 × 78 × 64 mm). In light of these findings, surgical intervention was recommended.

A right upper pole nephrectomy was performed via an open approach through an anterolateral lumbotomy incision ( Figs. 2 and 3 ). On anatomopathological examination, the hemi-nephrectomy specimen was occupied by a cyst with a whitish-colored, sclerotic-consistency wall. This cyst was capped by a crescent of renal tissue measuring 0.6 cm in thickness. Serial sectioning of the wall of this cyst revealed a second cyst with a lumen filled with a yellowish-white paste-like substance. The larger cyst had an internal surface lined with a multi-layered epithelium, often of the transitional type and focally keratinized squamous type. The rest of the cyst wall was composed of fibrous tissue rich in smooth muscle cells. The smaller cyst showed features of a dermoid cyst, with a lumen filled with keratin and desquamated squamous cells. Its wall was lined with an epidermis-like epithelium and contained hair follicles and sebaceous glands ( Fig. 4 ). Surrounding these cysts, connective and adipose tissue was observed, containing another cyst lined with squamous epithelium and tubules concentrically surrounded by cellular connective tissue resembling renal dysplasia ( Fig. 5 ). Additionally, the renal tissue identified macroscopically showed no lesions.