Expression of Cell-Cell Adhesion Molecules in Matrical Tumors of Hairs, Nails, Teeth and Pituitary Gland - Adhesion Molecules - page 299

(Gat et al. 1998). Activated nuclear β-catenin is also involved in the development of
tumors of the teeth (Sekine et al. 2003, Kumamoto and Ooya 2005), and pituitary
craniopharyngiomas (Sekine et al. 2002).

MATRICAL TUMORS: PHENOTYPE AND
NOMENCLATURE

Matrical tumors of the hair, nails, teeth and pituitary gland are usually described
separately in pathology topics (Rosai 2004). However, because those tumors have
similar histological features, they are grouped together in this chapter (Table 1) . We
propose that classii cation of some tumors on the basis of phenotype and oncogenic
signaling pathways (Table 2) rather than tissue of origin may be important for the
understanding of their biology and management.

Table 1 Nomenclature of matrical tumors from hairs, nails, teeth and pituitary gland

Hair Nails Teeth Pituitary gland

Pilomatricoma Onychomatricoma Calcifying odontogenic Craniopharyngioma

cyst

Matricoma Unguioblastoma Ameloblastoma

Pigmented matricoma Unguioblastic i broma Extraosseous ameloblastoma

Melanocytic matricoma
Pilomatrix carcinoma

h e nomenclature of matrical tumors of hair (Ackerman et al. 1993), nails (Baran and Kint 1992, Ko et al. 2004), teeth
(Neville et al. 2002) and pituitary gland (Rosai 2004) is based on their histological appearance.

Matrical Hair Tumors

Matrical hair tumors comprise pilomatricoma, matricoma, pilomatrix carcinoma
and melanocytic matricoma. Pilomatricomas are by far the most common of
the group. Pilomatricomas are composed of basaloid cells and 'shadow' fully
dif erentiated anucleated cells. h e lesions have a tendency to become cystic and
to calcify and ossify (Ackerman et al. 1993). An architectural variant with a more
pronounced dif erentiation towards the hair follicle inner sheath has been named
matricoma (Ackerman et al. 1993). Aggressive and coni rmed malignant variants
have been described under the name of pilomatrix carcinoma (Ackerman et al.
1993). Melanocytic matricoma is a more rare neoplasm thought to recapitulate
the bulb of the hair follicle in anagen (Ackerman et al. 1993). In addition to the
epithelial hair matrix cells and the terminally dif erentiated 'shadow' cells, there
is a conspicuous population of S-100, HMB45, and vimentin-positive pigmented
dendritic melanocytes, which dif erentiate it from pilomatricomas, matricomas
(Ackerman et al. 1993) and pigmented matricoma variants (Peralta Soler et al.
2007).