Case report: adrenal oncocytoma associated with markedly increased FDG uptake and immunohistochemically positive for GLUT1

Prognosis of Adrenal Oncocytic Neoplasms (AONs): Literature Review of 287 Cases and Presentation of the Oldest Patient

INTRODUCTION

The adrenocortical oncocytic neoplasms (AONs) are rare tumors of the adrenal gland, classified as oncocytoma (AO), oncocytic neoplasm of uncertain malignant potential (AONUMP) and oncocytic carcinoma (AOC). The aim of this study was to perform a review of the literature, in order to evaluate the prognosis of these rare cancers. We also reported the oldest patient with AON.

METHODS

A comprehensive literature review using as key words "adrenal oncocytoma", "adrenal oncocytic neoplasm", and "adrenal oncocytic carcinoma" was performed.

REPORT OF THE CASE

We report the case of an 88-year-old woman receiving a left open adrenalectomy for an AON (15 × 10 × 8 cm). The considerable size and weight together with the presence of necrosis were indicative for a lesion with an uncertain potential for malignancy, according to Weiss modified criteria. After two years, the patient was free from any sign of recurrence.

RESULTS

Only 287 AONs were detected in the scientific literature, exploring OVID, MEDLINE, PubMed and SCOPUS as dataset. These tumors are usually incidentalomas with an unpredictable malignant potential. Surgical resection remains the mainstay of treatment for AON.

CONCLUSION

AO and AONUMP have an excellent prognosis and a low mortality rate, with only three cases of recurrence reported in the literature and one metastatic case four years after first adrenal surgery. In contrast, AOC carries a high risk of local relapses, distant metastasis, and a significantly higher mortality rate (30%). Surgical resection remains the primary treatment for adrenal oncocytic neoplasms.

Oncocytic adrenocortical neoplasm with undetermined malignant potential and autonomous cortisol secretion

Increasing incidence of adrenal incidentalomas with hypercortisolemia not associated with overt features of Cushing's syndrome has led to the evolution of the term autonomous cortisol secretion. Oncocytic adrenocortical neoplasms (OANs) are rare adrenal cortex neoplasms with only 250 reported cases worldwide. We present a woman in her 30s with menometrorrhagia, weight gain and increasing abdominal girth who was found to have a large right adrenal mass on abdominal CT scan. Serum cortisol was not suppressed after 1 mg dexamethasone (31.5 µg/dL) and adrenocorticotrophic hormone was not detectable (<1.0 pg/mL). She underwent right adrenalectomy under glucocorticoid coverage. Hypertension, weight, visceral adiposity and menometrorrhagia improved postoperatively. Histopathology with immunohistochemistry showed OAN with undetermined malignant potential. These kinds of tumours can only be definitively diagnosed postsurgically using the Lin-Weiss-Bisceglia system. Although they have better prognosis compared with adrenocortical carcinomas and do not require chemotherapy, patients should be closely monitored to identify recurrence promptly.

Oncocytic Adrenocortical Carcinoma With Low 18F-FDG Uptake and the Absence of Glucose Transporter 1 Expression

Adrenocortical carcinoma (ACC) is a rare tumor, and some histological variants (oncocytic, myxoid, and sarcomatoid ACCs) have been reported in addition to the conventional ACC. Among these subtypes, oncocytic ACC is histologically characterized by the presence of abundant eosinophilic granular cytoplasm in the carcinoma cells owing to the accumulation of mitochondria, which generally yields high ¹⁸F-fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET). Herein, we report the case of a 21-year-old woman with oncocytic ACC with low FDG uptake on PET scan. Her circulating levels of androgens were high, and androgen-synthesis enzymes were detected in carcinoma cells. The patient also had hypocholesterolemia. However, glucose transporter 1 (GLUT1) was not detected in the tumor, which was considered to account for the low FDG uptake by the tumor. To the best of our knowledge, this is the first case of low FDG uptake by oncocytic ACC without GLUT1 expression. Additionally, since hypocholesterolemia was reported in 3 previous reports of androgen-producing tumors, a possible correlation between androgenicity in adrenal tumors and the development of hypocholesterolemia could be postulated; however, further investigations are needed for clarification. This case highlights important information regarding the diversity of ACC and its impact on hypocholesterolemia.

Adrenocortical oncocytic neoplasm: A systematic review

BACKGROUND

Adrenocortical oncocytic neoplasms are rare tumors, generally regarded as benign and hormonally nonfunctional. We performed a systematic review to update the literature on adrenocortical oncocytic neoplasms by reviewing patient and tumor characteristics, as well as management trends, because the literature is composed of predominately single-case reports.

METHODS

A systematic search was performed in PubMed, Embase, and Cochrane Library through June 2017. Malignant potential was determined by applying the Lin-Weiss-Bisceglia criteria to cases.

RESULTS

Included for analysis were 84 citations describing 140 adrenocortical oncocytic neoplasms, including our own case. These were diagnosed predominantly in females (66%), on the left side (64%), and were nonfunctional (66%). Average age at diagnosis was 44 years (2.5-77), and median tumor size was 80 mm (16-285). A total of 35% of adrenocortical oncocytic neoplasms were benign, 41% borderline, and 24% malignant. Male patients were more likely to have a malignant tumor compared with females (36% versus 18%, P = .035). The 5-year overall survival for benign adrenocortical oncocytic neoplasms was 100%, borderline 88%, and malignant 47%. Hormonal function did not discriminate malignant from benign lesions. Adrenocortical oncocytic neoplasms that stained positive for synaptophysin (50%, P < .001) and negative for vimentin (62%, P = .009) are more often benign.

CONCLUSION

We found that the majority of adrenocortical oncocytic neoplasms (65%) were either malignant or had malignant potential, contrary to the previous literature. The Lin-Weiss-Bisceglia criteria are useful in identifying those patients for whom closer surveillance is warranted, because their prognosis is dependent on the Lin-Weiss-Bisceglia diagnosis.