Seminoma with conspicuous signet ring cells: a rare, previously uncharacterized morphologic variant

Area of Science:

• Uropathology
• Oncology
• Cell Biology

Background:

• Seminoma is the most common type of testicular germ cell tumor.
• Morphological variations in seminoma can sometimes lead to diagnostic challenges.
• Signet ring cells are typically associated with other malignancies, not commonly described in seminoma.

Purpose of the Study:

• To describe two cases of seminoma with a prominent presence of signet ring cells.
• To detail the morphological and immunohistochemical features of these signet ring cells.
• To compare the prevalence of signet ring cells in these cases with a general seminoma population.

Main Methods:

• Histopathological examination of two testicular tumor samples.
• Periodic acid-Schiff (PAS) staining with and without diastase digestion.
• Immunohistochemical staining for mucicarmine, cytokeratin (AE1/3), alpha-fetoprotein, OCT3/4, and CD117.
• Review of 30 randomly selected seminomas for the presence of signet ring cells.

Main Results:

• Two seminomas, one pure and one mixed germ cell tumor component, showed conspicuous signet ring cells (10% and 70%).
• Signet ring cells contained cytoplasmic vacuoles, with one case showing glycogen deposits (PAS-positive, diastase-sensitive).
• Immunohistochemistry confirmed signet ring cells were negative for mucicarmine, cytokeratin, and alpha-fetoprotein, but positive for OCT3/4 and CD117.
• Rare, inconspicuous signet ring cells were found in 43% of 30 randomly selected seminomas.

Conclusions:

• Prominent signet ring cells in seminoma are rare but represent a potential diagnostic pitfall, possibly mimicking metastatic disease.
• The described signet ring cells share immunophenotypic characteristics with typical seminoma cells.
• This finding expands the known morphological spectrum of seminoma, aiding in accurate diagnosis.