Clinicopathological and immunohistochemical analysis of epithelial-lined (true) cysts of the adrenal gland with proposal of a new histogenetic categorization

Adrenal cysts: an emerging condition

Adrenal cysts are rare lesions representing approximately 1-2% of adrenal incidentalomas. The majority of these rare lesions are benign. Rarely, phaeochromocytomas and adrenal malignant masses can present as cystic lesions and can occasionally be difficult to distinguish from benign cysts. Histologically, adrenal cysts are subdivided into pseudocysts, endothelial cysts, epithelial cysts and parasitic cysts. The radiological appearance of an adrenal cyst is generally similar to that of cysts in the kidney. They are thus well demarcated, usually rounded, with a thin wall and homogenous internal structure, low attenuating (<20 Hounsfield Units) on CT, low signalling on T1-weighted MRI sequences and high signalling on T2-weighted MRI sequences, and anechoic or hypoechoic on ultrasonography. Benign adrenal cysts have a slight female predominance and are usually diagnosed between the ages of 40 and 60. Most adrenal cysts are asymptomatic and are detected incidentally, although very large adrenal cysts can lead to mass effect symptoms, with surgery required to alleviate the symptoms. Thus, conservative management is usually recommended for asymptomatic cysts. However, when uncertainty exists regarding the benign nature of the cyst, additional work-up or follow-up is needed. The management of an adrenal cyst should preferably be discussed at an adrenal multidisciplinary team meeting.

Observations on the origin of ovarian cortical inclusion cysts in women undergoing risk-reducing salpingo-oophorectomy

AIMS

Evidence suggests that up to 70% of high-grade serous ovarian carcinomas (HGSCs) arise potentially from fallopian tube fimbriae, and that many of the remaining cases arise from within the ovary in cortical inclusion cysts (CICs) with a Müllerian phenotype (Müllerian-CICs). It has been proposed that Müllerian-CICs arise either from metaplasia of mesothelial ovarian surface epithelium (OSE) entrapped within the ovary after ovulation or from normal tubal cells entrapped postovulation. However, this proposal is controversial. We therefore conducted a study of CICs in women, most of them BRCA1/2 mutation carriers, undergoing risk-reducing salpingo-oophorectomy at our institution from 2000 to 2014.

METHODS AND RESULTS

We used immunohistochemistry for PAX8, a Müllerian marker, and calretinin, a mesothelial marker to classify CIC cells. In 499 CICs from 59 women, 72.3% were positive for PAX8 (PAX8⁺ ): ≥10% of CIC cells positive; 43.5% positive for calretinin (calretinin⁺ ). The proportion of PAX8⁺ CICs increased from 62.9% in premenopausal to 80.5% in postmenopausal patients. The proportion of calretinin⁺ CICs decreased from 52.6% to 35.6%, respectively. There was significant overlap of PAX8 and calretinin positivity: 82 (16.4%) CICs were PAX8⁺ /calretinin⁺ ; 43 (40.2%) of these 82 demonstrated PAX8⁺ /calretinin⁺ in the same cells.

CONCLUSIONS

These results, and the increased ratio of PAX8⁺ to calretinin⁺ CICs from premenopausal to postmenopausal, show that many PAX8⁺ CICs probably arise from metaplasia of OSE-derived CICs. The proportion of PAX⁺ /calretinin^- CICs arising from OSE-derived CICs is unclear, but our results strongly support the proposal that many Müllerian-CICs arise from OSE via metaplasia.