Folliculocentric squamous cell carcinoma with tricholemmal differentiation: a reappraisal of tricholemmal carcinoma.
BACKGROUND
The diagnostic criteria for tricholemmal carcinoma remain controversial, and even the existence of tricholemmal carcinoma has been the subject of debate. Follicular (infundibular) squamous cell carcinoma (SCC) is a distinctive subset of SCC, which develops solely with folliculocentricity, and displays the features of conventional SCC without tricholemmal differentiation.


OBJECTIVE
To examine the existence of pure folliculocentric SCCs showing tricholemmal differentiation, that is, tricholemmal carcinoma.


METHODS
In total, 812 SCCs were examined, and those meeting the following diagnostic criteria were selected: (i) pure folliculocentricity without any associated Bowen's disease or actinic keratosis; (ii) composition primarily of lightly eosinophilic cells or clear cells containing glycogen; (iii) columnar lightly eosinophilic or clear cells aligned in a palisade along a discernible basement membrane; (iv) tricholemmal keratinization; (v) glycogen contained within the pale/clear cells; and (vi) cytological atypia and or infiltrative growth. We also evaluated whether the immunohistochemical profile [cytokeratin (CK)1, CK10, CK17, CD34 and D2-40] seen in normal hair follicles was retained in the selected lesions.


RESULTS
Only two lesions met the criteria. The immunohistochemical profile of the normal outer root sheath cells was generally retained in these lesions, except for CD34.


CONCLUSIONS
Tricholemmal carcinoma is a rare occurrence, but it does exist, and at least one type of tricholemmal carcinoma is considered to be related to follicular (infundibular) SCC.
Division of Dermatology, Department of Internal Medicine, Saga University, Saga, Japan. misago@post.saga-med.ac.jp
N
N
Misago
S
S
Toda
Y
Y
Narisawa
D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D007633:Keratins / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology*
D014408:Biomarkers, Tumor; D007633:Keratins