Histiocytoid Sweet syndrome: a dermal infiltration of immature neutrophilic granulocytes.
OBJECTIVE
To describe a series of 41 patients with fresh lesions of Sweet syndrome in which the histopathologic study demonstrated an inflammatory infiltrate mostly composed of histiocytoid mononuclear cells.


METHODS
Histopathologic, immunohistochemical, and cytogenetic studies of the inflammatory infiltrate in a case series of histiocytoid Sweet syndrome.


METHODS
University departments of dermatology and a private laboratory of dermatopathology.


METHODS
Conventional histopathologic study as well as immunohistochemical investigations were performed using the alkaline phosphatase antialkaline phosphatase technique with a large panel of antibodies. In some cases, fluorescent in situ hybridization studies were performed to investigate the presence of the bcr/abl gene fusion.


RESULTS
Immunohistochemical studies demonstrated that most cells of the infiltrate showed immunoreactivity for CD15, CD43, CD45, CD68, MAC-386, HAM56, and lysozyme, which is consistent with a monocytic-histiocytic immunoprofile. However, intense myeloperoxidase reactivity was detected in most of the cells with histiocytic appearance, which raised the possibility of specific cutaneous involvement by myelogenous leukemia. Nevertheless, cytologic peripheral blood examinations, fluorescent in situ hybridization studies to investigate the bcr/abl gene fusion, and follow-up of the patients, taken all together, ruled out this possibility.


CONCLUSIONS
This case series demonstrates that some fresh cutaneous lesions of Sweet syndrome are histopathologically characterized by an infiltrate mostly composed of cells that may be misinterpreted as histiocytes, when in fact they are immature myeloid cells. We named this histopathologic variant histiocytoid Sweet syndrome, which should not be mistaken with leukemia cutis or other inflammatory dermatoses that are histopathologically characterized by histiocytes interstitially arranged between collagen bundles of the dermis.
Requena
Luis
L
Department of Dermatology, Fundación Jiménez Díaz, Universidad Autónoma, Madrid, Spain. lrequena@fjd.es
Kutzner
Heinz
H
Palmedo
Gabriele
G
Pascual
Marta
M
Fernández-Herrera
Jesús
J
Fraga
Javier
J
García-Díez
Amaro
A
Yus
Evaristo Sánchez
ES
D000082:Acetaminophen / Q000008:administration & dosage; D000284:Administration, Oral; D000328:Adult; D000368:Aged; D001707:Biopsy, Needle; D015331:Cohort Studies; D004008:Diclofenac / Q000008:administration & dosage / Q000031:analogs & derivatives*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D005500:Follow-Up Studies; D006644:Histiocytes / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008875:Middle Aged; D011241:Prednisone / Q000008:administration & dosage; D012720:Severity of Illness Index; D016463:Sweet Syndrome / Q000188:drug therapy* / Q000473:pathology*; D016896:Treatment Outcome
D004008:Diclofenac; D000082:Acetaminophen; C056498:aceclofenac; D011241:Prednisone