In 1992, Sau and colleagues described 14 cases of a rare cutaneous adnexal tumor with differentiation toward the hair germ epithelium. All cases in their study displayed a unique constellation of histological features which allowed the authors to consider the neoplasm to be a distinct entity and to designate it as ‘trichogerminoma’ (TG). We present a case of an adnexal tumor identical to that described as TG and report the immunophenotypical features of this neoplasm for the first time. A biopsy from a 41-year-old man revealed a well-demarcated epithelial tumor composed of multiple lobules located in the deep dermis without connection to the overlying epidermis and surrounded by a fibrous pseudocapsule. The tumorous lobules were composed of uniform basophilic cells with vesicular nuclei, dispersed chromatin and prominent nucleoli showing no prominent peripheral palisading. Some of the lobules had the appearance of densely packed ‘cell balls’ with peripheral condensation of the tumor cells. The stroma showed a moderate number of fibroblasts and mast cells. Reticulum staining revealed fine reticulum fibers surrounding the tumor aggregates with accentuation of the ‘cell balls’. Immunohistochemically, the tumor cells expressed AE1/AE3, CK5/8, CK5/6, CAM5.2 and stained negatively for CK20, CK7, calretinin, Lu-5 and Thomsen- Friedensreich antigen. There was no increase in the numbers of CK20-positive Merkel cells in the epidermis overlying the tumor; however, a few Merkel cells were scattered in some tumor lobules. In addition, we stained 6 trichoblastomas (TBs) and found a particular pattern of calretinin expression in this tumor which was not observed in our case of TG. We conclude that pathological features allow the delineation of TG as a distinct adnexal neoplasm. Histological differential diagnosis includes basal-cell carcinoma (pilar type), large nodular TB, trichoblastic fibroma, trichoepithelioma, tricholemmoma, pilomatricoma and matrical carcinoma.

1.
Sau P, Lupton GP, Graham JH: Trichogerminoma: Report of 14 cases. J Cutan Pathol 1992;19:357–365.
2.
Weedon D: Skin Pathology. New York, Churchill Livingstone, 1997.
3.
Wick MR, Swanson PE, Barnhill RL: Tumors with hair follicle and sebaceous differentiation; in Barnhill RL (ed): Textbook of Dermatopathology. New York, McGraw-Hill, 1998, pp 593–621.
4.
Taaffe A, Wyatt EH, Bury HPR: Pilomatrixoma (Malherbe): A clinical and histological survey of 78 cases. Int J Dermatol 1988;27:477–480.
5.
Kaddu S, Soyer HP, Cerroni L, Salmhofer W, Hodl S: Clinical and histopathological spectrum of pilomatricoma in adults. Int J Dermatol 1994;33:705–708.
6.
Kaddu S, Soyer HP, Hodl S, Kerl H: Morphological stages of pilomatricoma. Am J Dermatopathol 1996;18:333–338.
7.
Ackerman AB, DeViragh PA, Chongchitnant N: Neoplasms with Follicular Differentiation. Philadelphia, Lea & Febiger, 1993.
8.
Weedon D, Bell J, Maize J: Matrical carcinoma of the skin. J Cutan Pathol 1980;7:39–42.
9.
Sau P, Lupton GP, Graham JH: Pilomatrix carcinoma. Cancer 1993;71:2491–2498.
10.
Schirren CG, Rütten A, Kaudewitz P, Diaz C, McClain S, Burgdorf WHC: Trichoblastoma and basal cell carcinoma are neoplasms with follicular differentiation sharing the same profile of cytokeratin intermediate filaments. Am J Dermatopathol 1997;19:341–350.
11.
Schirren CG, Burgdorf WHC, Sander CA, Plewig G: Fetal and adult hair follicle: An immunohistochemical study of anticytokeratin antibodies in formalin-fixed and paraffin-embedded tissue. Am J Dermatopathol 1997;19:334–340.
12.
Yamamoto O, Asahi M: Cytokeratin expression in trichoblastic fibroma (small nodular type trichoblastoma), trichoepithelioma and basal cell carcinoma. Br J Dermatol 1999;140:8–16.
13.
Schulz T, Hartschuh W: Merkel cells in nevus sebaceus: An immunohistochemical study. Am J Dermatopathol 1995;17:570–579.
14.
Schulz T, Hartschuh W: Merkel cells are absent in basal cell carcinomas but frequently found in trichoblastomas: An immunohistochemical study. J Cutan Pathol 1997;24:14–24.
15.
Collina G, Eusebi V, Capella C, Rosai J: Merkel cell differentiation in trichoblastoma. Virchows Arch 1998;433:291–296.
16.
McNiff JM, Eisen RN, Glusac EJ: Immunohistochemical comparison of cutaneous lymphadenoma, trichoblastoma, and basal cell carcinoma: Support for classification of lymphadenoma as a variant of trichoblastoma. J Cutan Pathol 1999;26:119–124.
17.
Poniecka AW, Alexis JB: An immunohistochemical study of basal cell carcinoma and trichoepithelioma. Am J Dermatopathol 1999;21:332–336.
18.
Kurzen H, Esposito L, Langbein L, Hartschuh W: Cytokeratins as markers for follicular differentiation: An immunohistochemical study of trichoblastoma and basal cell carcinoma. Am J Dermatopathol 2001;23:501–509.
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