A Case of Trichogerminoma

Trichogerminoma is a rare neoplasm which was first described in 1992 and there is still controversy over its inclusion into the spectrum of trichoblastoma. A 79-year-old woman presented with a 5-year history of an asymptomatic nodule on the left posterior neck. Histologically, the lesion revealed a well-demarcated deep dermal nodule surrounded by a pseudocapsule. The tumor was composed of lobules with basophilic cells and some of the lobules displayed a distinctive pattern of densely packed 'cell balls' with peripheral condensation. Immunohistochemically, the tumor cells showed zonal CK5/6 immunoactivity in contrast with the negatively stained 'cell balls'. These characteristics were compatible with the diagnosis of trichogerminoma. We report here on a rare case of a hair germ tumor called trichogerminoma.

Pigmented Trichogerminoma: A Case Report

Trichogerminoma is a rare cutaneous adnexal tumor that dysplays differentiation toward the hair germ epithelium. This tumor was first described by Sau et al. in 1992 and it is characterized by densely packed round nests or cell balls resembling hair bulbs. Herein, we report on a deeply pigmented and sharply circumscribed nodular tumor that was excised on the abdomen of a 48-year-old woman. Histologically the tumor involved both dermis and subcutis without any epidermal connection. The main nodule was subdivided into the smaller lobules by fibrous stroma. The lobules were composed of masses of basaloid cells that displayed peripheral palisading. Within the lobules, the basaloid cells formed numerous cell balls. The tumor presented the characteristic features of trichogerminoma. Interestingly, our case was the pigmented type, which was remarkable by virtue of the heavy melanin deposits found within and around the tumor nests. To the best of our knowledge, this is the first case of pigmented trichogerminoma that has been reported worldwide.

Trichogerminoma: A case report

Though trichogenic tumors were classified as trichoblastoma, trichoblastic fibroma, trichogenic trichoblastoma and trichogenic myxoma by Headington(1970), their true classification depends upon the epithelial and mesodermal component as well as evidence of their induction. Because of the rarity of hair germ cell tumors their classification is still controversial. In this report, we describe a case of trichogerminoma which is not included in the above classification. The trichogerminoma was first described by Sau et al. in 1992 and characterized by its morphologic pattern of germinal centers and lymphoid follicle-like structures in the nests of trichoblasts. Herein we reporte a tumor which arose on the skin on the back of a 51-year-old man and presented as a sharply circumscribed mass(4.5x2.0x1.5 cm) involving both the dermal and subcutaneous tissues without any epidermal connection. The tumor had many germinal center-like structures in the basaloid trichoblasts. Lobular cell nests were separated by variable amounts of stroma, but no horn cyst were noted. The germinal center-like cells showed early differentiation of hairs, resembling early hair bulbs. Trichogerminoma is considered to be a type of tumor located between trichoblastoma and trichoblastic fibroma.

Morphological Observations on the Hair Development of Human Fetal Skin

The developing process of the hair of the fetal skin was studied. The ages of 103 human embryos and fetuses ranged from 4 to 40 gestation weeks. Ten different sites were selected, i.e., scalp, forehead, cheek, chest, abdomen, back, palm, sole, finger and toe. For the embryos 3 sites were studied, i.e., cephalic, trunk, and caudal portions. Following results were made: 1) The primitive hair germ was first noted the 10th week in the face skin as nubbins of mesenchymal cells beneath discrete foci of crowdes, elongated germinative epithelial cells. The developing hair germs and hair pegs were observes at the cephalic portion by 11 weeks. At 15 weeks the hair pegs including hair germs were noted in the trunk skin. The bulbous hair peg stage started at the 16th week in the cephalic portion and at the 18th week in the trunk. 2) Relative number of fetal hairs progressively increase up to 20 weeks of gestation but, thereafter decreased although it was different by the site of the body. 3) The diameter of fetal hair follicles increased with fetal age to the term with slight difference by the portion of body. 4) The developmental process of hair was more rapid in the cephalic portion than the trunk in views of morphologic changes of the hair structures, number and diameter of hair follicles.