Chondroid syringoma. Cytokeratin 20 immunolocalization of Merkel cells and reappraisal of apocrine folliculo-sebaceous differentiation.
BACKGROUND
Chondroid syringoma (CS) is a benign cutaneous adnexal tumor with epithelial and stromal components. Epithelial components derived from folliculo-sebaceous-apocrine germ are evident in apocrine but not in eccrine CS.


OBJECTIVE
To further characterize pilosebaceous differentiation and to identify the presence of Merkel cells in the areas of follicular differentiation.


METHODS
Histologic type, folliculo-sebaceous differentiation, character of stroma, and presence or absence of Merkel cells by cytokeratin (CK) 20 immunoreactivity were evaluated in 25 CSs (22 apocrine and 3 eccrine) from the surgical pathology files of Henry Ford Hospital (Detroit, Mich).


RESULTS
Most CSs occurred in the head and neck region of patients aged 40 years or older. We found no significant difference in sex, age, or location between apocrine and eccrine types. The stroma varied from myxoid (100%) to chondroid (59%), with various amounts of fat (59%) and ossification identified in 2 cases (9%) of apocrine type, but was homogeneously myxoid in the eccrine type. Follicular and sebaceous differentiation was found in 64% and 32% of apocrine CSs, respectively. Only 2 (14%) apocrine CSs with follicular differentiation were positive for CK20 (a few scattered cells in one case and numerous grouped cells in the other in association with follicular epithelium). No correlation was found between type of stroma and the presence of Merkel cells. Scattered Merkel cells were identified in 83% of normal hair follicles and in 33.3% of normal epidermis.


CONCLUSIONS
A high proportion of apocrine CSs show folliculo-sebaceous differentiation. The presence of Merkel cells in foci of follicular differentiation of CS supports the hypothesis that Merkel cells may be an integral constituent of follicles. To our knowledge, the presence of Merkel cells in CS, particularly in proliferative form, has not been described previously in the literature.
Salama
Mohamed E
ME
Department of Pathology, Henry Ford Hospital, Detroit, Mich 48202, USA.
Azam
Muhammad
M
Ma
Chan K
CK
Ormsby
Adrian
A
Zarbo
Richard J
RJ
Amin
Mahul B
MB
Lee
Min W
MW
D008949:Adenoma, Pleomorphic / Q000737:chemistry / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001050:Apocrine Glands / Q000166:cytology; D002454:Cell Differentiation; D004439:Eccrine Glands / Q000166:cytology; D005260:Female; D018859:Hair Follicle / Q000166:cytology; D006258:Head and Neck Neoplasms / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D007381:Intermediate Filament Proteins / Q000032:analysis*; D053554:Keratin-20; D008297:Male; D018862:Merkel Cells / Q000737:chemistry / Q000473:pathology*; D008875:Middle Aged; D012627:Sebaceous Glands / Q000166:cytology; D012878:Skin Neoplasms / Q000737:chemistry / Q000473:pathology*; D013544:Sweat Gland Neoplasms / Q000473:pathology
D007381:Intermediate Filament Proteins; C507499:KRT20 protein, human; D053554:Keratin-20