Pseudoangiomatous Stromal Hyperplasia-Like Change in Mixed Epithelial and Stromal Tumor of the Seminal Vesicle: A Case Report Expanding the Morphologic Spectrum With 19-Year Follow-Up.
Ayaka Fukui, Yuki Teramoto, Nanako Izumi et al.
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Case in brief
A 70-year-old man had a low-grade mixed epithelial and stromal tumor (MEST) of the seminal vesicle. Needle biopsy showed interconnecting slit-like spaces in keloid-like collagen, lined by bland spindle cells and lacking erythrocytes; this raised concern for a vascular or sarcomatous neoplasm. The resection specimen revealed the biphasic architecture of MEST. Spindle cells were CD34-positive and CD31- and ERG-negative, supporting a myofibroblastic pseudovascular process rather than endothelial differentiation. After complete excision, the patient remained recurrence-free for 19 years.
What made this case unusual
The stromal component showed pseudoangiomatous stromal hyperplasia (PASH)-like change, a morphology not previously reported in seminal vesicle MEST. On biopsy, this pattern mimicked a vascular or sarcomatous neoplasm.
Diagnostic / clinical pearl
In a biopsy with slit-like spaces in collagen, assess for the biphasic architecture of MEST and use targeted immunohistochemistry: CD34 positivity with CD31 and ERG negativity supported pseudovascular myofibroblastic change in this case.
Why it matters
Recognizing this pattern may help resolve the differential diagnosis and avoid overgrading when biopsy material limits assessment of the tumor’s architecture.