Update: Myelolipoma Management

Hormonal Evaluation

• Modern guidelines recommend hormonal evaluation in masses diagnosed as myelolipomas on imaging.[1], [2] Some explicitly recognize the possibility of “myelolipomatous degeneration” of benign adrenal masses,[2] where as in others the recommendation is made as a blanket statement for all benign adrenal masses.[1]

• This recommendation differs from statements made in older, out-dated guidelines.[3]

Imaging

• The presence of an “large” area of visible fat attenuation within an adrenal lesion is universally considered to be 100% specific for benign pathology (almost always myelolipoma) within the guidelines.[1], [2], [4] Series also suggest that this finding is 100% sensitive.[5]

• The Canadian guidelines are the only guidelines to discuss this recommendation in any detail. 

• Even these guidelines state that the are of fat attenuation should be “large” and should be “isoattenuating to the retroperitoneal fat” without offering stricter definitions. [2]

• In one series, areas of myelolipoma considered by expert radiologists to be of “fat attenuation” ranged from -130 to -23 HU (mean -74 HU).[5] A cutoff of -30 HU has been proposed.[6] 

• In most cases of adrenal myelolipoma >50% of the lesion is fat attenuation, so the finding rarely ambiguous.[5] Defining a minimum amount of fat attenuating area that must be seen to make the diagnosis is therefore unlikely to be helpful. 

• There have been 7 total cases reported in the literature of an adrenocortical carcinoma containing macroscopic fat. [7]

• In each of these cases, fat comprised <5% of the total mass and the masses were symptomatic at presentation. 

• There are case series which include myelolipomas occurring within (or co-occurring with) other benign adrenal pathology, including those resulting from congenital metabolic abnormalities (e.g. congenital adrenal hyperplasia) and adrenal adenomas, which supports our recommendation above that patients with suspected myelolipoma should undergo hormonal workup. In these cases, the amount of macroscopic fat is usually less than 20% of the total size of the lesion.[5], [8]

Treatment

Additional Work Up

• When hormonal evaluation and imaging are suggestive of myelolipoma, no additional workup is required prior to observation or excision. (No guideline states this explicitly, but we are not aware of any paper which recommends a further work up.)

Treatment

• The only guidelines to specifically address this subject, written by the American Association of Endocrine Surgeons, explicitly recommends against resection of any myelolipoma unless it is causing symptoms due to mass effect.[9]

• Myelolipoma carries a small risk of spontaneous retroperitoneal hemorrhage, and thus some individual papers advocate prophylactic surgical resection of large myelolipomas, with various groups proposing cutoffs of 7cm[6], 8cm[10], and 10cm[5]. There are approximately 24 total cases of retroperitoneal hemorrhage associated with myelolipoma in the literature, with the smallest myelolipoma associated with hemorrhage measuring 7cm in diameter.[11]  In one series the size of tumors presenting with hemorrhage ranged from 8.5cm – 18.0cm with a mean of 14.2cm.[5] The severity of clinical presentation in these cases is unclear, though we are not aware of a reported case of death and transfusion appears uncommon.  

• Only one set of guidelines specifically addresses the need for follow up imaging of adrenal myelolipoma, and the recommendation is against any follow up imaging.[2] The American College of Radiology White Paper similarly recommends no follow up imaging for definitively benign lesions. This specifically includes myelolipomas, however there is no specific discussion or rationale given.[4] 

• In the largest reported series of follow up of myelolipoma, which consists of only 13 patients, only half increased in size at all. Follow up was too short and change in size too variable to make any meaningful statements about growth rates in those that did grow.[12] 

Follow Up

• Recurrence of myelolipoma following resection has not been reported. Therefore, we recommend no dedicated follow up imaging, although no published guidelines have specifically addressed this. 

Last update: 4/21/2024, Marshall Strother

[1] M. Fassnacht et al., “Management of adrenal incidentalomas: European Society of Endocrinology Clinical Practice Guideline in collaboration with the European Network for the Study of Adrenal Tumors,” Eur. J. Endocrinol., vol. 175, no. 2, pp. G1–G34, Aug. 2016, doi: 10.1530/EJE-16-0467.

[2] N. E. Rowe et al., “Canadian Urological Association guideline: Diagnosis, management, and followup of the incidentally discovered adrenal mass,” Can. Urol. Assoc. J., vol. 17, no. 2, pp. 12–24, Jan. 2023, doi: 10.5489/cuaj.8248.

[3] M. A. Zeiger et al., “American Association Of Clinical Endocrinologists And American Association Of Endocrine Surgeons Medical Guidelines For The Management Of Adrenal Incidentalomas,” Endocr. Pract., vol. 15, no. 1, pp. 1–20, Jul. 2009, doi: 10.4158/EP.15.S1.1.

[4] W. W. Mayo-Smith et al., “Management of Incidental Adrenal Masses: A White Paper of the ACR Incidental Findings Committee,” J. Am. Coll. Radiol., vol. 14, no. 8, pp. 1038–1044, Aug. 2017, doi: 10.1016/J.JACR.2017.05.001/ATTACHMENT/02189FE3-BE1D-4C85-B47B-305168681F5C/MMC1.DOCX.

[5] P. J. Kenney, B. J. Wagner, P. Rao, and C. S. Heffess, “Myelolipoma: CT and pathologic features,” Radiology, vol. 208, no. 1, pp. 87–95, 1998, doi: 10.1148/RADIOLOGY.208.1.9646797.

[6] S. Daneshmand and M. L. Quek, “Adrenal myelolipoma: diagnosis and management.,” Urol. J., vol. 3, no. 2, pp. 71–4, 2006.

[7] D. S. Ranathunga, L. A. Cherpak, N. Schieda, T. A. Flood, and M. D. F. McInnes, “Macroscopic Fat in Adrenocortical Carcinoma: A Systematic Review,” https://doi.org/10.2214/AJR.19.21851, vol. 214, no. 2, pp. 390–394, Nov. 2019, doi: 10.2214/AJR.19.21851.

[8] J. Guccione et al., “Imaging characteristics of pathologically proven adrenal adenomas with myelolipomatous degeneration: correlation with clinical and pathologic features,” Br. J. Radiol., vol. 95, no. 1129, 2022, doi: 10.1259/BJR.20210555.

[9] L. Yip et al., “American Association of Endocrine Surgeons Guidelines for Adrenalectomy: Executive Summary,” JAMA Surg., vol. 157, no. 10, pp. 870–877, Oct. 2022, doi: 10.1001/jamasurg.2022.3544.

[10] V. M. Gershuni, J. G. Bittner, J. F. Moley, and L. M. Brunt, “Adrenal Myelolipoma: Operative Indications and Outcomes,” J. Laparoendosc. Adv. Surg. Tech. A, vol. 24, no. 1, p. 8, Jan. 2014, doi: 10.1089/LAP.2013.0411.

[11] V. G. Shenoy, A. Thota, R. Shankar, and M. G. Desai, “Adrenal myelolipoma: Controversies in its management,” Indian J. Urol. IJU J. Urol. Soc. India, vol. 31, no. 2, p. 94, Apr. 2015, doi: 10.4103/0970-1591.152807.

[12] M. Han, A. L. Burnett, E. K. Fishman, and F. F. Marshall, “The natural history and treatment of adrenal myelolipoma.,” J. Urol., vol. 157, no. 4, pp. 1213–6, Apr. 1997.