ELSEVIER
Annals of Diagnostic Pathology
journal homepage: www.elsevier.com/locate/anndiagpath
Annals of DIAGNOSTIC PATHOLOGY
Original Contributions
Myxoid adrenocortical adenoma with pseudoglandular pattern: A clinicopathological study of a rare histologic variant and its diagnostic challenges
Runlin Feng ª,1, Tao Zhang b,1, Changxing Keb,*, Yanping Taoc, **
a Department of Pathology, The Second Affiliated Hospital of Kunming Medical University, Kunming 650101, Yunnan, China
b Department of Urology, The Second Affiliated Hospital of Kunming Medical University, Kunming 650101, Yunnan, China
” Department of Emergency, Kunming Third People’s Hospital, Yunnan, China
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ARTICLE INFO
Keywords:
Myxoid adrenocortical adenoma Pseudoglandular pattern Adrenal tumor
Weiss score, immunohistochemistry Mucinous neoplasms
ABSTRACT
Objective: Myxoid adrenocortical adenoma (MAA) with a pseudoglandular pattern is a rare variant of adrenal cortical tumors, characterized by a prominent myxoid matrix and diverse architectural patterns. Due to its overlapping features with malignant and metastatic myxoid tumors, it poses significant diagnostic challenges. This study aimed to delineate the clinicopathologic, immunohistochemical, and differential diagnostic features of MAA based on a case series.
Methods: We retrospectively analyzed nine cases of MAA diagnosed between 2015 and 2023. Comprehensive clinicoradiologic, histopathologic, and immunophenotypic data were collected. Histologic evaluation included Weiss scoring, mitotic activity, and reticulin framework analysis. Immunohistochemistry was performed using a panel of markers including «-inhibin, Melan-A, Synaptophysin, CD56, CK, Vimentin, S100, and HMB45. Alcian blue and AB-PAS staining were applied to assess mucin content. All cases were followed for postoperative outcomes.
Results: The cohort included 5 females and 4 males, with a median age of 40 years (range 27-53). Tumor sizes ranged from 2.2 to 7.4 cm (mean 4.1 cm). Grossly, all tumors were well-demarcated, solid, and mucin-rich without evidence of necrosis or vascular invasion. Histologically, all cases exhibited abundant extracellular myxoid stroma (mean proportion: 78.3 %) and diverse pseudoglandular, cord-like, and sieve-like architectures. Tumor cells were polygonal with eosinophilic or hyaline cytoplasm and minimal atypia. No mitotic figures >2/ 20 HPF were observed. Immunohistochemistry showed diffuse positivity for a-inhibin (100 %), Melan-A (88.9 %), CD56 (77.8 %), Synaptophysin (66.7 %), and Vimentin (100 %), while S100, HMB45, and Chromogranin A were consistently negative. Ki-67 index was <3 % in all cases. Alcian blue was strongly positive in 77.8 % of tumors, supporting the myxoid component. During a median follow-up of 14 months, no recurrence or metastasis occurred.
Conclusions: MAA with a pseudoglandular pattern is a benign but diagnostically challenging adrenal neoplasm due to its histologic overlap with myxoid adrenal cortical carcinoma and metastatic mucinous tumors. Recog- nition of its characteristic morphology, immunoprofile, and benign clinical course is critical to prevent over- treatment. Incorporating Weiss criteria, reticulin staining, and a myxoid tumor differential panel enhances diagnostic accuracy in clinical practice.
1. Introduction
Myxoid adrenocortical adenoma (MAA) with a pseudoglandular
pattern is a rare histologic variant of adrenocortical neoplasms, exhib- iting prominent extracellular myxoid stroma and diverse architectural growth patterns such as pseudoglandular, trabecular, and sieve-like
* Correspondence to: C. Ke, Department of Urology, The Second Affiliated Hospital of Kunming Medical University, Kunming, China.
** Correspondence to: Y. Tao, Department of Emergency, The Third People’s Hospital of Kunming, Kunming, China. E-mail addresses: kenne126@126.com (C. Ke), tao87yao@163.com (Y. Tao).
1 These authors contributed equally to this work.
https://doi.org/10.1016/j.anndiagpath.2025.152527
arrangements. This tumor was first recognized by Tang et al. in 1979 and subsequently described in greater morphologic detail by Dundr et al. in 2003 [1-3]. Despite these early reports, MAA remains unclassified in current WHO endocrine tumor classifications and is frequently under- recognized in diagnostic practice due to its nonspecific radiologic and clinical features.
MAAs typically occur in middle-aged adults without sex predilection and are often non-functional, detected incidentally during imaging or physical examinations. Imaging studies usually reveal well- circumscribed, solid adrenal masses with heterogeneous enhancement, which may mimic pheochromocytoma, adrenal cortical adenoma, or metastatic tumors [4-6]. Due to the lack of specific biochemical or radiologic markers, definitive diagnosis of MAA relies heavily on his- topathologic and immunophenotypic analysis.
Histologically, MAAs are characterized by a rich basophilic myxoid matrix and tumor cells arranged in pseudoglandular or retiform pat- terns. The degree of mucinous degeneration varies between cases, often occupying over 60 % of the tumor volume. This histological feature presents a significant diagnostic pitfall, as it closely resembles that of myxoid adrenal cortical carcinoma, metastatic mucinous adenocarci- noma, and soft tissue sarcomas with myxoid stroma, such as chordoma, myxoid liposarcoma, and myxofibrosarcoma [7-9]. Thus, appropriate immunohistochemical profiling is essential.
Immunophenotypically, MAAs consistently express adrenal cortical markers such as a-inhibin, Melan-A, and Synaptophysin, while negative for S100, HMB45, and Chromogranin A. The Ki-67 proliferation index is usually below 3 %, consistent with benign behavior. Application of the Weiss scoring system, along with reticulin framework integrity assess- ment, further supports the benign nature of MAA and aids in dis- tinguishing it from adrenocortical carcinoma [10-12].
To date, most literature on MAA consists of single-case reports, lacking standardized diagnostic criteria or long-term follow-up. Very few studies have systematically analyzed clinicopathologic, radiologic, and immunohistochemical characteristics in a cohort setting. Moreover, the correlation between mucinous content and tumor function or clinical outcome remains largely unexplored.
In this study, we retrospectively analyzed nine histologically confirmed cases of MAA with a pseudoglandular pattern. We aimed to define its clinicopathologic features, immunohistochemical profile, and key differential diagnostic criteria. We also applied established patho- logic scoring systems (Weiss, reticulin) to evaluate the biological behavior of these tumors. Our findings may help raise awareness of this rare variant and offer practical guidance for accurate diagnosis and classification in daily pathology practice.
2. Materials and methods
2.1. Study design
This retrospective study included nine patients diagnosed with MAA with a pseudoglandular pattern between January 2015 and July 2023 at the Second Affiliated Hospital of Kunming Medical University. All cases were retrieved from the institutional pathology archive and indepen- dently reviewed by three board-certified pathologists with expertise in endocrine pathology. Tumors were included if they demonstrated extensive extracellular myxoid stroma (at least 60 % of the tumor vol- ume), architectural patterns such as pseudoglandular, sieve-like, or trabecular arrangements, and histologic features consistent with benign behavior. Cases with confirmed adrenal cortical carcinoma, metastatic lesions, or limited diagnostic tissue were excluded. Final diagnoses were rendered after comprehensive evaluation of gross, microscopic, and immunohistochemical findings. All procedures adhered to the ethical principles of the Declaration of Helsinki and its later amendments.
2.2. Clinical and radiological evaluation
Demographic and clinical data, including age, sex, clinical presen- tation, hormonal status, imaging findings, surgical procedures, and follow-up information, were obtained from electronic medical records. All patients underwent preoperative imaging with computed tomogra- phy (CT) or magnetic resonance imaging (MRI), and all radiologic di- agnoses were confirmed by two experienced radiologists specializing in adrenal imaging.
2.3. Gross and histopathologic evaluation
Surgical specimens were fixed in 10 % neutral buffered formalin, embedded in paraffin, and sectioned at 4 pm. Hematoxylin and eosin (H&E) staining was performed in all cases. Tumor architecture, cyto- logic features, presence of myxoid matrix, mitotic activity (per 20 high- power fields), capsular and vascular invasion, and background adrenal tissue were systematically assessed.
The Weiss scoring system was applied to evaluate the malignant potential of each tumor, with a total score < 3 interpreted as consistent with adenoma. Reticulin staining using Gomori’s method was performed in all cases to assess the integrity of the reticulin fiber network. A pre- served reticulin framework supported a benign diagnosis, whereas dis- rupted or incomplete reticulin networks were considered suggestive of malignancy.
2.4. Immunohistochemistry
Immunohistochemical staining was performed on representative tumor sections using an automated platform (Ventana Benchmark ULTRA, Roche Diagnostics). The antibody panel included a-inhibin, Melan-A, Synaptophysin (SyN), CD56, Cytokeratin (CK), Vimentin, Neuron-specific enolase (NSE), Chromogranin A (CgA), S100, and HMB45. All antibodies were sourced from Fujian Maixin Biotechnology Co., Ltd., and validated controls were included for each run.
Staining intensity and proportion were assessed independently by two experienced pathologists in a double-blind manner. Immunoreac- tivity was defined as positive if >10 % of tumor cells showed cyto- plasmic or membranous staining. Staining intensity was scored semi- quantitatively as negative (-), weakly positive (+), moderately posi- tive (++), or strongly positive (+++). The Ki-67 index was calculated by counting at least 1000 tumor cells in the highest proliferative area.
2.5. Special stains
Alcian blue (pH 2.5) and Alcian blue-periodic acid-Schiff (AB-PAS) staining were used to evaluate extracellular mucin deposition. Myxoid matrix was defined as Alcian blue-positive, AB-PAS-negative or focally positive material diffusely distributed within the tumor interstitium.
2.6. Follow-up
All patients were followed postoperatively through hospital records and telephone interviews. Data on recurrence, metastasis, and survival were collected at the most recent follow-up (range: 5 to 36 months, median: 14 months). No patients received preoperative chemotherapy, radiotherapy, or targeted therapy.
3. Results
3.1. Clinical findings
A total of nine patients were included, comprising five females and four males, with a mean age of 40 years (range: 27-53 years). Six tumors were located in the right adrenal gland and three in the left. The ma- jority of cases (n = 6, 66.7 %) were incidentally detected during routine
physical examinations. The remaining three patients presented with nonspecific symptoms, including abdominal discomfort (n = 2) and newly diagnosed hypertension (n = 1). Four patients had a history of hypertension and one had coexisting hyperthyroidism. No patients re- ported features of overt hormone excess, and all were clinically non- functional based on endocrinologic evaluations. All the patients were followed up for an average of 14 months (ranging from 5 to 36 months). No tumor recurrence and no metastasis were observed, and all patients survived to the last date of follow-up.
3.2. Radiological findings
Preoperative imaging was performed in all nine patients, including seven computed tomography (CT) scans and two magnetic resonance imaging (MRI) studies. On CT, the tumors appeared as well- circumscribed, low-density nodules with heterogeneous enhancement in four patients, initially suggestive of pheochromocytoma or non- functional adenoma. In two cases, CT revealed irregular soft-tissue masses with inhomogeneous enhancement, interpreted as neurogenic tumors(Fig. 1). MRI findings in the remaining two patients showed well- demarcated lesions with slightly hyperintense T2 signals and iso- to hypointense T1 signals, further supporting a differential diagnosis of pheochromocytoma(Fig. 2).None of the imaging studies indicated ma- lignancy or extra-adrenal extension.
3.3. Gross pathology
Tumor size ranged from 2.2 to 7.4 cm, with a mean diameter of 4.1 cm. Seven tumors were solitary and two were multinodular. The ma- jority displayed smooth, well-defined borders (7/9), while two tumors had slightly irregular or indistinct margins. The cut surfaces were pale yellow to grayish-yellow, variably translucent, and gelatinous in appearance. Two tumors exhibited gray-brown jelly-like consistency. Capsular invasion was observed focally in two cases but without extracapsular extension or adjacent organ involvement. None of the tumors showed evidence of hemorrhage, necrosis, cystic degeneration, or vascular invasion (Supplementary Table 1).
3.4. Histopathological features
All tumors demonstrated extensive extracellular myxoid stroma, accounting for 60 %-90 % of the tumor area (mean: 78.3 %). Tumor cells were predominantly arranged in pseudoglandular, trabecular, cord-like, and sieve-like architectures. The neoplastic cells were polyg- onal with well-defined borders, abundant eosinophilic or clear cyto- plasm, round-to-oval nuclei, and inconspicuous nucleoli. Mitoses were rare, with counts ranging from 0 to 1 per 20 high-power fields. No sig- nificant pleomorphism, necrosis, or atypical mitotic figures were observed. Classical adrenocortical adenoma components were observed interspersed within the myxoid matrix in five cases. Reticulin staining demonstrated preserved reticulin fiber architecture in all tumors (Fig. 3A-F), consistent with benign cortical origin. Weiss scores ranged
from 0 to 2, supporting the diagnosis of adrenocortical adenoma.
3.5. Immunohistochemical profile
Representative immunostaining patterns are shown in Fig. 4, con- firming consistent expression of cortical markers. Immunohistochemical findings are summarized in Supplementary Table 2. All tumors showed strong positivity for «-inhibin (9/9) and diffuse expression of Vimentin in stromal regions. Melan-A was positive in eight cases (88.9 %), and CD56 in seven (77.8 %), while Synaptophysin was strongly positive in six (66.7 %). Cytokeratin was expressed in four tumors (44.4 %). NSE was focally positive in three tumors. All cases were negative for S100, Chromogranin A (CgA), HMB45, and CR, effectively excluding pheo- chromocytoma, melanocytic, or metastatic components. Alcian blue staining was diffusely positive in seven tumors (77.8 %), whereas AB- PAS staining was only focally positive in one case (11.1 %). The Ki-67 labeling index was consistently low, ranging from 1 % to 2 %, sup- porting indolent biological behavior.
3.6. Follow-up outcomes
All nine patients underwent complete surgical excision with negative margins. No perioperative complications were reported. During a me- dian follow-up period of 14 months (range: 5-36 months), no recur- rence, metastasis, or mortality was observed. All patients remained alive and disease-free at last follow-up, supporting the benign nature of MAA with a pseudoglandular pattern.
4. Discussion
In this analysis of nine cases, we found that MAA with pseudo- glandular architecture consistently presented benign clinicopathologic features. None of the tumors displayed Weiss scores ≥3, disrupted reticulin framework, or Ki-67 indices >3 %, and all patients remained disease-free over a median follow-up of 14 months. These findings reinforce MAA as a benign entity distinguishable by classic adrenal cortical marker expression (a-inhibin, Melan-A) and absence of aggres- sive histologic traits.
Our series, one of the most extensive to date, adds depth to the limited reports of MAA (~20 cases) in the literature [6,13]. While prior studies described solitary cases or small series without systematic follow-up, our cohort provides structured long-term data. Recent up- dates to the WHO adrenal tumor classification continue to recognize myxoid features in cortical carcinomas but have yet to formalize criteria for benign myxoid adenomas, underscoring a critical gap we begin to address.
The presence of retained reticulin networks and low mitotic activity (0-1/20 HPF) were pivotal in diagnosing adenoma rather than carci- noma. These criteria are consistent with multiparameter schemes endorsed by the 2022 WHO, including the reticulin algorithm and Helsinki score [6,14]. Ki-67 values <3 % align with benchmarks dis- tinguishing carcinoma (≥5-10 %) in recent studies [15]. This triple
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A. The tumor cells were dense and diffusely distributed.
B. The tumor tissue was distributed in a nodular pattern.
C. Residual adrenocortical tissue was seen around the tumor cells.
D. Normal adrenal cortex was seen interspersed between tumor cells within the tumor parenchyma.
E. The tumor cells were arranged in a pseudoadenoidal pattern with hyaline cell cytoplasm.
F. The tumor was tubular and staggered, and a large amount of mucus-like material was seen within the cells.
G. The tumor cells were arranged in a pseudoadenoid pattern, and the cells had eosinophilic cytoplasm.
H. A large amount of mucus-like material extravasates outside the cell, caused by intra- and extracellular mucus.
I. Under high magnification, the cells were round with dark chromatin, and small nucleoli were visible.
assessment-Weiss, reticulin, and Ki-67-aligns with current adrenal pathology best practices and reliably indicates benign behavior.
Accurate diagnosis of MAA requires careful distinction from several histologically and immunophenotypically overlapping entities, partic- ularly those with abundant myxoid stroma or pseudoglandular features. Failure to differentiate these lesions correctly may lead to overtreatment or misclassification. The most clinically significant differential is myx- oid adrenocortical carcinoma (ACC), a rare but aggressive malig- nancy. Unlike MAA, myxoid ACC often presents with large tumor size,
Fig. 4. Immunohistochemical phenotypic characteristics of patients. A. CD56 showed positive expression (immunohistochemistry, scale 50 um). B. CK showed positive expression (immunohistochemistry, scale 50 um). C. HMB45 showed negative positive expression (immunohistochemistry, scale 50 um). D. a-inhibin showed positive expression (immunohistochemistry, scale 50 um). E. SyN showed positive expression (immunohistochemistry, scale 50 um). F. S100 showed negative expression (immunohistochemistry, scale 50 um). G. NSE showed positive expression (immunohistochemistry, scale 50 um). H. Melan-A showed positive expression (immunohistochemistry, scale 50 um). I. VIM showed positive expression (immunohistochemistry, scale 50 um).
necrosis, marked cytologic atypia, increased mitotic activity (≥5/10 HPF), and vascular invasion [16,17]. Histologically, although both tu- mors may exhibit abundant myxoid matrix, ACC demonstrates an infiltrative growth pattern and commonly lacks a preserved reticulin network. Moreover, a high Ki-67 proliferation index (>10 %), as well as p53 overexpression or aberrant ß-catenin staining, are more frequently associated with malignancy [18-21]. These features were uniformly absent in our series, supporting a benign diagnosis. Further- more, metastatic mucinous adenocarcinomas, particularly those originating from the gastrointestinal tract (e.g., colorectal or pancre- atic), can mimic the pseudoglandular and mucin-rich appearance of MAA. However, such metastases typically express CK20, CDX2, or TTF- 1, and lack adrenal-specific markers such as a-inhibin, Melan-A, and SF-1 [22-24]. Radiologic context and systemic workup are essential
adjuncts in such cases, especially when bilateral adrenal involvement or concurrent primary neoplasms are detected. In contrast, primary soft tissue myxoid tumors, such as myxoid liposarcoma, chordoma, and myxofibrosarcoma, may involve the retroperitoneum and exhibit deceptively bland morphology. These tumors often express lineage- specific markers like S100, SOX10, MUC4, Brachyury, or desmin, which are consistently negative in MAA [25-28]. Importantly, these neoplasms frequently demonstrate aggressive clinical behavior, with a propensity for local recurrence and metastasis, further underscoring the necessity of immunohistochemical confirmation. Another important differential is primary adrenal cortical neoplasm with pseudo- glandular pattern but lacking myxoid features, which can include conventional adenomas with acinar or nested growth. These lesions may raise concern in small biopsies or limited sections. However, the extensive myxoid stroma and mucin-like matrix seen in MAA serve as critical discriminators. Additionally, a preserved reticulin framework remains a cornerstone for distinguishing benign from malignant adrenal cortical tumors, as endorsed by the 2022 WHO classification [6,29]. Lastly, rare adrenal oncocytomas or mixed-pattern adrenal tumors can occasionally present with architectural complexity. Yet, their cyto- plasmic eosinophilia, nuclear atypia, and lack of myxoid change effec- tively separate them from MAA. Ki-67 and reticulin status further assist in their evaluation [30-33].Taken together, integrating histomorphol- ogy with a targeted immunohistochemical panel-including a-inhibin, Melan-A, SF-1, CK7/20, S100, and Ki-67-provides a robust strategy to accurately distinguish MAA from its benign and malignant mimickers. This diagnostic precision is crucial to avoid misdiagnosis and unnecessary radical interventions.
This study’s strengths include its integrative approach to diagnosing pseudoglandular MAA, systematic use of current scoring systems, and long-term follow-up data. We provide a reproducible diagnostic algo- rithm suitable for clinical practice: tumors with abundant myxoid stroma, preserved reticulin, low mitotic and Ki-67 indices (<5 %), and strong adrenal marker expression should be classified as benign. Such clarity may prevent overtreatment of these rare tumors and supports their formal recognition in authoritative tumor classification systems.
This study has several inherent limitations that should be acknowl- edged. First, due to the rarity of myxoid adrenocortical adenoma (MAA), our sample size was relatively small and derived from a single institu- tion, potentially limiting the generalizability of our findings. Although all tumors displayed indolent behavior over a median follow-up of 14 months, this relatively short observation period may not be sufficient to capture late recurrences or rare malignant transformations. Moreover, while the diagnostic approach based on histopathology and immuno- histochemistry was comprehensive, the absence of molecular profi- ling-such as targeted sequencing of CTNNB1, TP53, or IGF2-precludes deeper insight into the genetic underpinnings of MAA. These molecular alterations have been increasingly recognized in adrenocortical tumors and may aid in stratifying borderline lesions or predicting biological behavior.
Future studies should aim to validate our proposed diagnostic criteria across multicenter cohorts with larger case numbers and extended follow-up durations. Incorporating genomic, transcriptomic, and methylation profiling could elucidate the molecular landscape of MAA and clarify its relationship to conventional adenomas or low-grade carcinomas. Additionally, prospective studies comparing MAA with its malignant mimickers-such as myxoid adrenocortical carcinoma or metastatic mucinous tumors-may yield valuable biomarkers for dif- ferential diagnosis. Development of machine learning-based histo- pathologic classifiers, trained on digitized whole-slide images, could further enhance diagnostic reproducibility and support integration into routine clinical workflows. Ultimately, establishing a consensus-based diagnostic algorithm for MAA will require interdisciplinary collabora- tion among pathologists, endocrinologists, and molecular biologists.
Myxoid adrenocortical adenoma with a pseudoglandular pattern is a rare but benign adrenal tumor that can be reliably diagnosed based on
reticulin framework integrity, low Ki-67 index, and specific immuno- profiles. Our findings help distinguish it from malignant mimickers and emphasize the importance of standardized histopathologic criteria. Further multicenter studies and molecular investigations are warranted to validate its biological behavior and diagnostic framework.
CRediT authorship contribution statement
Runlin Feng: Conceptualization, Data curation, Methodology, Su- pervision, Writing - original draft, Writing - review & editing. Tao Zhang: Data curation, Investigation, Methodology, Supervision, Writing - original draft, Writing - review & editing. Changxing Ke: Conceptu- alization, Investigation, Methodology, Writing - review & editing. Yanping Tao: Conceptualization, Data curation, Methodology, Super- vision, Writing - review & editing.
Ethical approval
The study was approved by the Ethics Committee of the Second Affiliated Hospital of Kunming Medical University, and the approval number was Review-PJ-Department-2023-296.
Fundings
This study was supported by the Yunnan Health Training Project of High-Level Talents (Approval Number: H-2024017), the Yunnan Fundamental Research Projects (Grant No .: 202501AT070489), and the Yunnan Fundamental Research-Kunming Medical University Joint Projects (Grant No .: 202401AY070001-080). Additional support was provided by the Talent Echelon Cultivation Project of the Second Affil- iated Hospital of Kunming Medical University, Yunnan Province (Project No .: RCTDHB-202305).
Declaration of competing interest
The authors declare that no competing interests exist.
Acknowledgments
The authors sincerely thank the Department of Pathology at the Second Affiliated Hospital of Kunming Medical University for their technical support, as well as the radiology and clinical teams for their collaboration in case retrieval and diagnostic confirmation.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi. org/10.1016/j.anndiagpath.2025.152527.
Data availability
The data that support the findings of this study are available from the corresponding author upon reasonable request.
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