Rarely a proliferation of histiocytes with a signet ring cell appearance may be seen in the sinuses of lymph nodes.
Significance: confusion with metastatic adenocarcinoma. This can be very important if the patient has a history of adenocarcinoma or during rapid intraoperative assessments.
Conditions associated with signet ring cell histiocytes:
(1) typhoid fever
(2) Kikuchi's lymphadenitis
(3) past infusion of IV fluid containing polyvinylpyrrolidone (PVP)
Histologic features of signet ring cells:
(1) nuclei do not show marked atypia
(2) cytoplasmic vacuoles may or may not stain for mucicarmine and/or periodic acid Schiff (PAS) stains
(3) cells are positive on immunohistochemical staining for histiocyte markers
(4) cells are negative on negative immunohistochemical staining for epithelial markers
(5) cells are negative on immunohistochemical staining for lymphoid markers
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