Primary adrenal melanoma: A case report and review of the literature

Background

Primary adrenal melanoma is extremely rare, currently with 23 cases in a literature review. ¹ Typically, patients present with abdominal symptoms such as flank pain^2–5 and weight loss.^3,5–8 In this paper, we present a case of primary adrenal melanoma, which initially presented with weight loss, abdominal bloating, distention, intermittent diarrhea, and flatulence, but no flank pain.

Case review

An 82-year-old male with a history of robotic-assisted laparoscopic prostatectomy for pT2N0 Gleason score 3+4 prostate cancer presented with abdominal bloating, distention, intermittent diarrhea, flatulence, and weight loss. The patient’s father had lung cancer, and his mother had a stroke. Under the working diagnosis of irritable bowel syndrome, the patient failed to improve on a gluten-free diet. Subsequently, computed tomography (CT) virtual colonoscopy discovered a large right upper pole renal mass without masses suggestive of primary colon carcinoma. A follow-up dedicated CT of the abdomen and pelvis confirmed a large 9.5 cm×7.2 cm×9.2 cm mass emanating from either the upper pole of the right kidney or the right adrenal gland (Figure 1). A nuclear bone scan and chest CT were negative for metastatic disease. A positron emission tomography scan showed a hypermetabolic mass from the right adrenal gland, with additional nonspecific hypermetabolic mediastinal and bilateral hilar lymph nodes (Figure 2). There was no biochemical evidence of a functional adrenal mass. His prostate serum antigen was undetectable. The patient had a Karnowski Performance Scale Index of 80, which signifies normal activity with effort with some signs or symptoms of disease. The patient reported no signs of vision change, and thus an ocular melanoma origin was not suspected. Furthermore, the patient reported no neurological deficits to suspect a leptomeningeal origin.

Figure 1.

Computed tomography (CT) of the abdomen and pelvis showing the right adrenal mass measuring 9.5 cm×7.2 cm×9.2 cm.

Figure 2.

Positron emission tomography scan showing the hypermetabolic mass on the right adrenal gland and nonspecific hypermetabolic mediastinal and bilateral hilar lymph nodes.

The patient underwent an open right adrenalectomy using a modified Makuuchi incision. A multidisciplinary team with hepatobiliary surgeons mobilized the entire right side of the liver, allowing for full exposure of the mass and adequate control of the inferior vena cava. The mass was significantly attached to a portion of the diaphragm, and thus we resected this en bloc with the mass. An intraoperative chest tube was placed. Estimated blood loss was 1000 mL. The patient experienced no postoperative complications and was discharged home on postoperative day 10.

The adrenalectomy specimen grossly showed a 12.5 cm ill-defined mass with a variegated, tan-to-brown, friable cut surface. Histological examination demonstrated sheets of high-grade tumor cells with prominent melanin pigmentation (Figure 3(a) and (b)). All surgical margins were negative for tumor. Immunohistochemical studies further revealed that the tumor cells were diffusely positive for SOX10 (Figure 3(c)), S-100 protein (Figure 3(d)), melan-A (Figure 3(e)) and HMB-45 (Figure 3(f)), and were negative for other proteins, including pan-cytokeratin, epithelial membrane antigen, chromogranin A, synaptophysin, CD56, inhibin, calretinin and Nkx3.1. A pathology departmental consultation and dermatopathology consult lead to the diagnosis of melanoma based on these findings. The patient had no history of melanoma and, after dermatologic examination, was found to have no suspicious skin lesions.

Figure 3.

Histopathology of the primary adrenal melanoma. Hematoxylin and eosin staining: (a) 100× and (b) 400×. Immunohistochemical labeling for (c) SOX10 (100×), (d) S-100 protein (100×), (e) melan-A (100×), and (f) HMB-45 (100×).

The patient is now six months out from surgery and has been seen in follow-up by medical oncology and dermatology without evidence of disease recurrence. Given his high risk of relapse, medical oncology started him on adjuvant nivolumab, which he is tolerating well overall.

Discussion

In the literature, there were two recent cases for a primary adrenal malignant melanoma. One involved a 58-year old man who felt left flank pain, and showed a large retroperitoneal tumor measuring 15.5 cm×12.1 cm×13.0 cm originating from the left adrenal gland. ⁹ In the other, a 58-year-old woman who had symptoms of asthenia, anorexia and weight loss presented with a retroperitoneal mass measuring 10 cm×15 cm originating in the left adrenal gland. ⁸ Based on a negative screen for a pigmented mucous, cutaneous, leptomeningeal or ocular lesion, we conclude that the patient likely had a primary adrenal melanoma. ⁶ From our findings, a primary adrenal melanoma should be considered in the differential diagnosis of a large adrenal mass. Other diagnoses within the differential include adrenal cortical tumors, adrenal cortical carcinoma, pheochromocytoma and solitary adrenal metastases. Based on the authors’ clinical reasoning, a functional adrenal cortical tumor or pheochromocytoma were less likely, given the negative biochemical workup. However, it was also possible, but not likely, that this could have represented a solitary metastatic lesion, given his history of prostate cancer based on the authors’ experience. While a biopsy could have been pursued, the patient’s care team decided the results were unlikely to change management in someone with a large retroperitoneal mass without evidence of metastatic disease and could have led to biopsy related complications. Regardless of the final pathology, the same surgical principles exist: adequate exposure and minimal tumor manipulation are paramount. As in this case, surgical expertise from different disciplines may be vital to maintain these surgical principals.

Once the diagnosis of melanoma is made, it is important for prompt referral to dermatology. Clinicians should also look for the two most common locations of non-cutaneous melanomas, which include ocular and mucosal melanomas. ¹ For the dermatologic evaluation, a good history and physical can help to rule out a cutaneous melanoma. With no ocular, mucosal or cutaneous lesions, a diagnosis of primary adrenal melanoma can be made. ⁶

Our case demonstrates another presentation of a primary adrenal melanoma. The strengths and weaknesses are like that of other case reports. This case report provides an in-depth study of the initial clinical symptoms, imaging, histology and even treatment of a rare disease. However, because this is only one case study and is relatively early patient’s recovery, we do not know the final outcome of the disease, regardless, timely surgical exploration is recommended for both diagnostic and therapeutic purposes. Interdisciplinary care to ensure complete surgical resection and adjuvant therapy may lead to better outcomes of this rare but highly lethal presentation of melanoma.