Pseudoendocrine sarcoma: a rare new entity with unique radiologic and pathologic/molecular characteristics.

Pseudoendocrine sarcoma is a rare, recently described intermediate grade sarcoma of uncertain phenotype that most commonly affects the paraspinal location in older patients with a distinctive endocrine/paraganglioma-like morphology and unique CTNNB1 point mutation. While these tumors appear as epithelial or even benign endocrine tumors, these lack markers for such and are highlighted by nuclear expression of beta-catenin. This case is the first among the previously reported only twenty-five cases of this entity, including one original series and a few case reports, to correlate the radiologic imaging with the pathologic features. Furthermore, this case illustrates the oldest-to-date patient with this unique location as a palpable painful chest wall/paraspinal location, with new morphologic observations and, finally, this is only the second case to have this specific CTNNB1 hotspot point mutation for this rare entity.

Case report: pseudoendocrine sarcoma, a clinicopathologic report of a newly described soft tissue neoplasm.

Papke et al. recently reported a series of twenty-three soft tissue lesions chiefly arising in older adults featuring distinct morphological and genetic characteristics. Pseudoendocrine sarcoma (PS) is the somewhat descriptive and provisional term adopted for the newly reported mesenchymal neoplasm. Since the publication of the original paper published in January 2022, a single case of PS has been published. Pseudoendocrine sarcoma shows a predilection for the paravertebral deep soft tissues of the trunk, low-grade neuroendocrine-like histological features, and hallmark CTNNB1 activating mutations.Herein, we will discuss a case of a 72-year-old woman presenting with a 4-cm laterocervical mass. Hematoxylin and eosin slides showed a multilobular proliferation of monomorphic epithelioid cells with speckled chromatin arranged in nests and trabeculae. Immunohistochemical staining and molecular analysis were consistent with the newly proposed entity.

Pseudoendocrine sarcoma: clinicopathologic, molecular, and epigenetic features of one case.

Pseudoendocrine sarcoma (PES) is a recently described neoplasm typically arising in paravertebral soft tissues. Histologically, PES resembles well-differentiated neuroendocrine tumors but lacks expression of epithelial/neuroendocrine markers, and most show aberrant nuclear ß-catenin positivity. We describe the clinicopathological and molecular features and DNA methylation profile of one PES. A resected paraspinal soft tissue mass in a 52-year-old man showed a neuroendocrine-like neoplasm, negative for keratin, and synaptophysin and showing diffuse nuclear ß-catenin expression. Targeted NGS confirmed a CTNNB1 (p.S37C) mutation. Whole genome methylation analysis showed no match to any methylation class in the central nervous system tumor (versions 11b6 and 12b6) or sarcoma classifier (calibrated scores of ≤0.3), but clustered together with a recently reported PES in which methylation analysis was also performed. He remained disease-free for 18 months after surgery, followed by chemoradiation. As more cases are examined, our findings suggest that PES may have a unique methylation profiling signature.