Myxoid adrenocortical adenoma with pseudoglandular pattern: A clinicopathological study of a rare histologic variant and its diagnostic challenges

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 α-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 α-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. Recognition of its characteristic morphology, immunoprofile, and benign clinical course is critical to prevent overtreatment. Incorporating Weiss criteria, reticulin staining, and a myxoid tumor differential panel enhances diagnostic accuracy in clinical practice.