Microscopic description and IHC:

The biopsy shows antral-type gastric mucosa with surface fibrin and reactive foveolar epithelium with mucin depletion. A few detached fragments on the mucosal surface contains clusters of epithelial cells with large eosinophilic cytoplasmic vacuoles and eccentric small nuclei, resembling signet ring cells. These cells are absent within the laminar propria or stroma.

The signet ring-like cells are positive for E-cadherin, CK7 (focal), CK20, and negative for p53, CDX2, GATA3, and estrogen receptor. The Ki67 proliferation index is less than 5%.

Discussion:

Signet-ring cell change (SCC) is a non-neoplastic condition that can morphologically simulates signet-ring cell carcinoma (SRCC). Aside from the different IHC profiles, the cells are bland, lack infiltrative pattern of SRCC. There is also a background of reactive gastropathy.

The pathogenesis of SCC is unclear. However cases of SCC associated with acute erosive gastropathy (such as this case!) and pseudomembranous colitis has been reported. Current literature suggests it can arise in the setting of ischemia, ulceration, or necrosis.

table depicting Signet-ring change
References:

Wang, Kim, et al. "Signet-ring cell change versus signet-ring cell carcinoma: a comparative analysis." The American journal of surgical pathology 27.11 (2003): 1429-1433.

Cameselle-Teijeiro, José, Ihab Abdulkader, and Jerónimo Forteza. "Signet-ring cell change in pseudomembranous colitis versus signet-ring cell carcinoma." The American journal of surgical pathology 28.8 (2004): 1111.

CASE IMAGES