PD-1, S-100 and CD1a expression in pseudolymphomatous folliculitis, primary cutaneous marginal zone B-cell lymphoma (MALT lymphoma) and cutaneous lymphoid hyperplasia.
BACKGROUND
Pseudolymphomatous folliculitis is a lymphoid proliferation that clinically and histopathologically mimics primary cutaneous extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma). In this study, we assessed the diagnostic value of three immunohistochemical markers, programmed death-1 (PD-1), CD1a and S100.


METHODS
We evaluated 25 cases of cutaneous lymphoid proliferations with established diagnoses, including 9 patients with pseudolymphomatous folliculitis, 11 with MALT lymphoma, and 5 with cutaneous lymphoid hyperplasia (CLH). The clinical, histopathologic and immunohistochemical characteristics were reviewed and three major characteristics assessed: (a) proportion of T cells expressing PD-1, (b) pattern of expression of CD1a by dendritic cells and (c) pattern of expression of S100 by dendritic cells.


RESULTS
We found pseudolymphomatous folliculitis to have a significant increase in PD-1+ T cells compared with MALT lymphoma (p < 0.0001). The pattern of CD1a staining is also informative: MALT lymphoma is significantly more likely to demonstrate a peripheral concentration of CD1a+ dendritic cells around lymphoid nodules than pseudolymphomatous folliculitis (p < 0.0003) or CLH (p < 0.05). Pseudolymphomatous folliculitis demonstrates an interstitial distribution of CD1a+ cells more often than MALT lymphoma (p < 0.04). S100 staining was not a helpful discriminator.


CONCLUSIONS
Histopathologic factors including PD-1 and CD1a staining patterns may allow for more certainty in distinguishing lymphoid hyperplasia, including pseudolymphomatous folliculitis, from MALT lymphoma.
Dermatopathology Unit, Massachusetts General Hospital, Boston, MA, USA.
Amrita
A
Goyal
Johanna B
JB
Moore
Devon
D
Gimbel
Joi B
JB
Carter
Daniela
D
Kroshinsky
Judith A
JA
Ferry
Nancy L
NL
Harris
Lyn M
LM
Duncan
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018949:Antigens, CD1 / Q000096:biosynthesis*; D014408:Biomarkers, Tumor / Q000096:biosynthesis; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D016393:Lymphoma, B-Cell / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D018442:Lymphoma, B-Cell, Marginal Zone / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D061026:Programmed Cell Death 1 Receptor / Q000096:biosynthesis*; D019310:Pseudolymphoma / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D009418:S100 Proteins / Q000096:biosynthesis*; D012871:Skin Diseases / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D012878:Skin Neoplasms / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D055815:Young Adult
D018949:Antigens, CD1; D014408:Biomarkers, Tumor; C419393:CD1a antigen; C105992:PDCD1 protein, human; D061026:Programmed Cell Death 1 Receptor; D009418:S100 Proteins
CD1a; MALT lymphoma; PD-1; lymphoid hyperplasia; pseudolymphomatous folliculitis