Applied Radiology

Prepared by Feng Tao, MD, Evan Mortan, MD, and Stephen C. Machnicki, MD from the Department of Radiology, and Ljiljana Vasovic, MD and Frank Breuer, MD from the Department of Pathology, Lenox Hill Hospital, New York, NY; and Richard A. Heiden, MD from the Department of Radiology, Interfaith Medical Center, Brooklyn, NY.

CASE SUMMARY

A 31-year-old woman with no significant past medical history presented to the gynecological service with right upper quadrant and mid-upper abdominal pain. On physical examination, cervical motion tenderness was induced. The patient was admitted to receive intravenous antibiotic treatment for presumed pelvic inflammatory disease. However, laboratory and radiological workup were subsequently negative and her symptoms quickly improved. A week later, she returned to surgical clinic complaining of recurrent right upper quadrant pain. A computed tomography (CT) scan revealed a large complex cystic lesion in the right upper quadrant. Further evaluation with magnetic resonance imaging (MRI) and ultrasound did not delineate the origin of the cyst clearly. Serological studies excluded the possibilities of echinoccocal disease.

An exploratory laparoscopy was performed. The postoperative course was uneventful, and the patient did well. Cytology of the aspirated fluid showed no malignancy or bile.

DIAGNOSIS

Right adrenal gland benign true cyst with degeneration and calcification

IMAGING FINDINGS

Computed tomography (figure 1) scan demonstrated an 8.0-cm thick-walled, multi-loculated cystic structure in the right suprarenal area, with calcifications.

Ultrasound (figure 2) demonstrated a bilobed cystic mass either adjacent to or in the posterior aspect of the right lobe of the liver. This complex cystic mass had thick walls, internal debris, and septations.

Magnetic resonance imaging (figure 3) demonstrated a large, complex bilobed cystic mass in the right upper quadrant measuring approximately 7.8 * 7.8 * 9.0 cm in antero-posterior, transverse, and craniocaudal dimensions, respectively. No normal right adrenal gland was identified. It was uncertain whether this mass arose from the right adrenal gland or from the right lobe of liver.

The radiological differential diagnosis included a hemorrhagic cyst, infectious cysts (such as a hydatid cyst or abscess from the adrenal gland or the right lobe of the liver), an adrenal pseudocyst, an adrenal true cyst, or cystic neoplasms of right adrenal gland (such as adrenal cortical adenoma, carcinoma, and pheochromocytoa).

Intraoperatively, a large cyst was found in the retroperitoneal space posterior to the right lobe of the liver. Clear yellow fluid was aspirated. The cyst was unroofed and partially removed. Gross pathological examination showed a cyst filled with proteinacious material. Microscopic examination of the cyst wall (figure 4) demonstrated adrenal cortical tissue and a broad zone of hyalinized collagen, which showed erosion, degeneration, calcification, and focal lymphocyte infiltration. A single layer of benign-appearing cuboidal cells with convex apical surface lined a portion of the inner surface of the cyst. Immunohistochemical studies revealed (figure 5) positive staining of these cuboidal cells for cytokeratin and calretinin, and negative for CD34, indicating a mesothelial origin.

DISCUSSION

Adrenal cysts are rare ¹ (0.064% to 0.18% in autopsy series), and fewer than 500 cases have been reported in the Western literature. Traditionally, adrenal cysts have been divided into four general groups ² : 1) endothelial lined cysts (45%); 2) pseudocysts (39%); 3) cysts secondary to infectious agents, such as echinococci; and 4) epithelial-lined or true adrenal cysts (9%). In addition, adrenal cystic neoplasm, dermoid cysts, and lymphangioma ^3-6 have been reported. Of these, endothelial-lined cysts and pseudocysts are most common and comprise approximately 90% of cases. Epithelial-lined true cysts are rare, and theoretically could be retention cyst (glandular), or arising from adrenal cortical adenoma and embryonal cyst. Some authors doubt the existence of true adrenal cyst. ⁷

Unfortunately, clinical and imaging findings alone, ^8,9 and even fine-needle aspiration, cannot always make the diagnosis and distinguish these lesions. Surgical biopsy is always needed. Therefore, adrenal cysts can present a difficult diagnostic problem. The importance of accurately diagnosing adrenal cysts lies in separating them from cystic lesions in adjacent organs (such as the kidneys, spleen, and liver), and predicting the benign or malignant nature of the lesion. Ultrasound, CT, and MRI ¹ have been reported to have diagnostic sensitivities of 66.7%, 80%, and 100%, respectively.

Retrospective review of the ultrasonographic features of adrenal lesions ¹⁰ revealed that focal absence of periglandular fat between the adrenal gland and the large vessels or liver, as well as deviation or compression of the large vessels by the adrenal lesion, may indicate malignancy. In addition, adrenal tumors, benign or malignant, were often associated with a prominent uterus, uterine stump, or prostate with or without prostatic cysts.

Evidence of lipid content of adrenal cysts is clearly demonstrated on ultrasound, CT, and MRI. ¹¹ Nevertheless, the histology type cannot be predicted.

A report of the MRI features of adrenal pseudocysts ¹² showed two components: 1) a large component with low signal intensity on both T1- and T2-weighted images and 2) a second, smaller, fluid component. These features are not specific, however, as an adrenal adenoma may have a similar appearance.

Previous experience demonstrates that a careful hormonal (for functional cyst), morpho-functional, and instrumental evaluation is indicated in all adrenal cysts, because even when the available diagnostic modalities are combined, they cannot always define the nature of these cysts. Surgical excision, when possible by laparoscopic approach, is indicated in the presence of symptoms, endocrine abnormalities (even when subclinical), complication and suspicion of malignancy, and/or large size (>5 cm). Such is also the case for cystic large adrenal adenoma, ¹³ which can present with a heterogeneous, more frequently calcified appearance.

The management of adrenal cysts depends on clinical and imaging findings and diagnosis. Symptomatic ones should be resected, but small, asymptomatic, non-functional cysts with benign characteristics may be treated conservatively with regular follow-up by sonography or CT and hormonal evaluation, ¹⁴ as malignant cystic tumors are uncommon. The finding of clear liquid and nonmalignant cell cytology practically excludes malignant tumors. ¹⁵ Furthermore, cystic adeno-carcinomas are usually large and the cystic fluid is cloudy with abundant cellularity.

Giant adrenal cysts are usually pseudocysts, ¹⁶ and these usually occur in elderly patients. However, a recent report showed giant adrenal cysts occurring in three teenage girls. ¹⁷

Adrenal cysts can be associated with certain medical conditions such as hepatic focal nodular hyperplasia, ¹⁸ hypertension, and pregnancy. ¹⁹ Co-existence of adrenal cystic lymphangiomas with nevoid basal cell carcinoma (Gorlin-Goltz) syndrome were reported with ultrasound and MRI findings. ²⁰

Finally, radiological differential diagnosis of adrenal cysts should always include cystic lesions in the adjacent organs such as the liver, spleen, and kidneys, cystic retroperitoneal tumors, and other rare congenital abnormalities, such as bronchogenic cysts. ²¹

In summary, a case of adrenal true (epithelial) cyst, a rare entity, is reported here with its radiological and pathological findings. The diagnosis of different types of adrenal cystic lesions and their differentiation from cystic lesions of the adjacent organs are critical for clinical management. The combination of clinical, laboratory, and imaging findings is essential. A few promising imaging and laboratory characteristics have been reported that may be of use in the diagnosis of adrenal cysts. It is important for the radiologist to be familiar with the characteristic appearances of different cystic adrenal lesions in order to guide diagnosis and patient management.