Oncocytic adrenocortical neoplasm of borderline uncertain malignant potential diagnosed after robot-assisted adrenalectomy case report

AONs are diagnosed via surgical pathology following adrenalectomy for presumed malignancy on cross-sectional imaging. The European Society of Endocrinology recommends laparoscopic adrenalectomy for suspected malignant tumors < 6 cm presenting without local invasion [3]. Retrospective evidence supports tumor size as a relative contraindication for minimally invasive adrenalectomy, with the primary concern being incomplete resection or capsular rupture causing local recurrence in large tumors suspected to be malignant [4,5,6]. However, the NCCN recommends that the surgical approach can be tailored to the surgeon’s technical experience [7]. Robotic surgery allows for better manipulation of fragile adrenal tissue and may decrease the risk of capsular rupture and incomplete resection by virtue of the high-definition three-dimensional view of the operative field and greater range of motion afforded than with laparoscopy or open approach [8]. We opted to perform this case robotically based on the extensive robotic experience of the surgeon and the belief that the potential benefits of decreased postoperative pain and shorter hospital stay vindicated the risks.

The crux of postoperative management in AON is the decision to initiate adjuvant therapy based on the histological criteria assessing malignant potential via either the Lin-Weiss-Bisceglia (LWB) system, reticulin algorithm, or the Helsinki scoring system [9, 10]. The LWB criteria designates an AON as malignant if the tumor meets any of the following major criteria: (1) mitotic rate of > 50 mitoses per 50 high-power field (HPF), (2) any atypical mitoses, (3) any venous invasion. AONs are classified as borderline with uncertain malignant potential (BUMP) if they meet one to four of the following minor criteria: (1) size > 10 cm and/or weight > 200 g, (2) presence of necrosis, (3) sinusoidal invasion, (4) capsular invasion. AONs are categorized as benign in the absence of major or minor criteria. The reticulin algorithm characterizes malignancy based on the presence of an altered reticulin framework demonstrated by histological stain as basis and combined with at least one of the following features: (i) the presence of mitotic rate > 5 mitoses per 50 HPF, (ii) tumor necrosis, or (iii) vascular invasion. Lastly, the Helsinki scoring system is a point-based risk stratification system. It awards 3 points if there are greater than 5 mitoses per 50 HPF, 5 points for the presence of necrosis, and adds the numeric values form the Ki67 index. A Helsinki score of 0-8.5 suggests adrenal cortical adenoma and a score > 8.5 is suggestive of of adrenal cortical carcinoma. The tumor in our report met 3 of the LWB minor criteria (size > 10 cm, necrosis, capsular invasion) and was thus classified as an AON with BUMP. This tumor also exhibited a patchy loss of reticulin framework paired with the presence of tumor necrosis, which may be suggestive of malignancy—though unclear, per the reticulin algorithm. The only scoring system that was suggestive of malignant potential was the Helsinki system score of 16 (Ki67 of 11% and tumor necrosis), The prognosis of AONs is a function of malignant potential: 5-year survival was estimated to be 100% for benign tumors, 88% for borderline tumors, and 47% for malignant tumors, per LWB classification [11]. We managed this patient under the assumption that this tumor was AON with BUMP, following multidisciplinary discussions.

If an AON is classified as malignant or BUMP, adjuvant mitotane chemotherapy and adjuvant radiation therapy is considered based on extrapolated data from patients with ACC. The European Society of Endocrinology clinical guidelines recommends against use of adjuvant radiation therapy for stage I and II disease with negative surgical margins. Recommendation for adjuvant mitotane is limited to ACC patients with high risk of recurrence based on data from retrospective analyses that demonstrated improved recurrence-free and overall survival [12]. Indicators of high recurrence risk include presence of Ki67 staining in > 10% of cells, > 20 mitotic figure per 50 HPF, intraoperative tumor spillage, and large tumors with vascular or capsular invasion [9]. The tumor in our case demonstrated Ki67 > 10% and capsular invasion. However, shared decision-making resulted in surveillance without adjuvant mitotane or radiation, given negative surgical margins, favorable prognosis of AONs with BUMP, and the unclear benefit of such therapy on the oncocytic variant of adrenocortical carcinoma.

There are no standard post-operative surveillance recommendations for AONs. Given AON with BUMP, we opted for CT scan every 3 months for up to 5 years informed by clinical guidelines for ACC follow-up [7]. However, limited evidence from systematic reviews suggests that in comparison to ACCs, AONs with BUMP have markedly better prognosis and lower rate of recurrence [11]. As more cases of AONs are reported, the optimal surveillance schedule for AONs based on malignant potential may be determined.

We present a case of a 15 cm AON with borderline uncertain malignant potential treated with robotic surgery and review the post-operative decision-making management criteria. AONs are rare, typically benign tumors that can be safely treated with robotic-assisted adrenalectomy. Surgical pathology is part and parcel of diagnosis and determines then neoplasm’s malignant potential, which may inform both the initiation of adjuvant therapy and the post-operative surveillance regimen.

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