Anatomic Imaging

ACC overview

Anatomic imaging in adrenocortical carcinoma (ACC) refers primarily to cross-sectional morphologic assessment with computed tomography (CT) and magnetic resonance imaging (MRI) to detect adrenal masses, characterize their structural features, and define local and regional extent of disease.¹ Within ACC care, it sits at the interface between initial adrenal mass evaluation, preoperative staging, and assessment of invasion that may alter resectability or operative planning. Typical imaging appearances may suggest malignancy, but anatomic imaging alone cannot definitively distinguish ACC from benign adenoma or from other malignant or noncortical adrenal-region lesions.¹²

The evidence base for this topic is uneven. Much of the practical framework is derived from broader adrenal imaging reviews, historical radiology experience, and retrospective morphologic interpretation rather than from prospective ACC-specific comparative studies.¹² As a result, imaging findings are most reliable for identifying lesion size, heterogeneity, necrosis, hemorrhage, mass effect, and venous or adjacent organ involvement, whereas tumor typing by morphology remains substantially less reliable.¹

This creates a characteristic limitation in ACC workup: anatomic imaging is central for defining anatomy and surgical context, but it usually contributes probability rather than certainty for diagnosis. Clinical implication therefore depends on the task being asked of imaging—recognizing a suspicious adrenal phenotype, mapping local invasion, or narrowing the differential within a broader multimodal evaluation.¹

Diagnostic context

Anatomic imaging is part of the standard structural assessment of an adrenal mass and is most informative when interpreted alongside endocrine testing, clinical presentation, and, when needed, functional imaging or other adjunctive studies.¹ Modern adrenal mass characterization relies on CT and MRI as the core modalities, particularly because they can localize the lesion, evaluate enhancement patterns, and assess surrounding structures in a way older localization methods could not reliably accomplish.²¹

Historically, radiologic evaluation of upper retroperitoneal masses demonstrated an enduring problem that still applies in modified form today: morphology alone may show displacement, compression, calcification, or venous obstruction without fully resolving tissue of origin or biologic behavior.² This historical context is reliable as a reminder of the limits of purely anatomic assessment; the practical implication is that suspicious imaging should be integrated into a broader adrenal diagnostic workflow rather than treated as a standalone diagnosis.²¹

Major imaging phenotypes

Suspicious CT and MRI appearance

ACC on anatomic imaging is generally approached as a large, heterogeneous adrenal mass that may contain necrosis, hemorrhage, irregular enhancement, and distortion of normal adrenal architecture. These features support suspicion for malignancy, especially when the lesion is bulky or invasive, but they are not pathognomonic for ACC and may overlap with other adrenal neoplasms or metastatic disease.¹

What is relatively reliable is that marked heterogeneity and aggressive local morphology increase concern for a malignant adrenal process. What is not reliable is confident histologic discrimination based on morphology alone; the clinical implication is that imaging can prioritize urgency and staging, but not replace definitive pathologic or multidisciplinary diagnostic assessment.¹

Differential diagnosis among adrenal and adrenal-region masses

A major use of anatomic imaging is to narrow the differential diagnosis of an adrenal mass rather than to label it definitively as ACC. In this setting, CT and MRI are commonly used to separate clearly benign lipid-rich adenoma from lesions that remain indeterminate or suspicious, while also considering pheochromocytoma, metastasis, lymphoma, hemorrhage, infection, myelolipoma, and other uncommon entities.¹

This differential framework is clinically important because a lesion that does not meet benign imaging criteria may still represent several non-ACC diagnoses. The reliable contribution of imaging is stratification into benign-appearing versus indeterminate or malignant-appearing patterns; the less reliable contribution is exact tumor typing, which often requires correlation with biochemical, oncologic, or surgical findings.¹

A similar principle extends to other morphologic modalities. Limited indirect evidence from ultrasonography supports the idea that structural abnormality, including altered gland size or shape, may indicate adrenal disease, but sonographic appearance alone does not reliably establish tumor type.³ The practical implication is that ultrasound may detect a mass or suggest venous involvement in selected settings, yet cross-sectional imaging and definitive tissue-based diagnosis remain more important in suspected ACC.³

Local invasion and venous extension

Once a lesion is considered suspicious for ACC, the next major task of anatomic imaging is to define local extent. This includes evaluation for renal vein or inferior vena cava extension, compression or invasion of adjacent organs, and superior propagation of tumor thrombus where present.² These findings are often more actionable than attempts at fine-grained morphologic diagnosis because they directly affect surgical planning and procedural risk.

Compared with lesion characterization, assessment of anatomic extent is a more reliable strength of CT and MRI. Imaging may still underestimate microscopic invasion, but it is generally better suited to identifying gross venous involvement, mass effect, and multivisceral relationships than to distinguishing ACC from competing histologies.²¹ The clinical implication is that imaging should be read not only for “what the mass is” but also for “where the disease goes,” especially when resection is being considered.

Limitations and interpretive pitfalls

The main limitation of anatomic imaging in ACC is overlap. Benign adenomas, pheochromocytomas, metastases, and other adrenal or retroperitoneal lesions may share some morphologic features with ACC, particularly when lesions are large or atypical.¹ Even when imaging is strongly suspicious, morphology alone cannot provide definitive confirmation of adrenocortical origin or malignant potential.

A second limitation is that portions of the literature are indirect or historical. Older radiology studies remain useful for illustrating localization and invasion problems, but they do not define modern diagnostic performance, and isolated case reports offer only weakly generalizable support for specific modalities or signs.²³ The practical implication is that individual imaging observations should be interpreted cautiously unless they align with broader contemporary adrenal imaging principles.¹

Role in management and research

In management, anatomic imaging contributes most clearly to initial staging logic, operative planning, and differential diagnosis within the adrenal mass workup.¹ It is therefore complementary to, rather than a substitute for, endocrine evaluation, pathologic confirmation when appropriate, and functional imaging in selected cases.¹

For research, the field remains constrained by limited ACC-specific prospective evidence and by dependence on broader adrenal imaging frameworks. Current synthesis suggests that the most clinically durable uses of anatomic imaging are structural characterization and mapping of disease extent, whereas precise noninvasive discrimination of ACC from other adrenal lesions remains an unresolved problem.¹²

Included Articles

• PMID 7852151: A ferret case report describes ultrasonographic detection of adrenal cortical carcinoma and emphasizes that gland size and shape are more informative than echogenicity alone, with histology required for confirmation. Its relevance to ACC is indirect but consistent with general limits of morphologic imaging in distinguishing adrenal malignancies.³

• PMID 14120791: A 1964 review of adult renal and suprarenal tumours describes the historical radiologic workup of adrenal-region masses and emphasizes that plain films and pyelography often could not confidently establish renal versus suprarenal origin. It also notes a role for venacavography in venous obstruction, adding historical context to modern anatomic differential imaging in ACC.²

• PMID 39794659: A 2025 review of adrenal imaging describes how CT, MRI, and nuclear medicine are integrated across the broad differential diagnosis of adrenal lesions. For ACC, its main relevance is the reminder that morphologic imaging is interpreted within a multimodal adrenal-mass workup rather than in isolation.¹

References

Footnotes

1. Advances in multimodal imaging for adrenal gland disorders: integrating CT, MRI, and nuclear medicine.. Jpn J Radiol. 2025. PMID: 39794659. Local full text: 39794659.md ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹

2. TUMOURS OF THE KIDNEYS AND SUPRARENALS. II. RENAL AND SUPRARENAL TUMOURS IN ADULTS.. Br J Radiol. 1964. PMID: 14120791. Local full text: 14120791.md ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰

3. Ultrasonographic detection of adrenal gland tumors in two ferrets.. J Am Vet Med Assoc. 1994. PMID: 7852151. Local full text: 7852151.md ↩ ↩² ↩³ ↩⁴