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Galli-Galli disease, a rare genodermatosis belonging to the spectrum of reticulate pigment dermatoses, is classified as an acantholytic variant of Dowling-Degos disease on the basis of its characteristic clinical and histological findings. In the context of this case series, Galli-Galli disease is characterized in detail based on the clinical and histopathological evaluation of 18 patients. The disease pattern is discussed in view of the current literature. In addition, a classification into two clinical subtypes is made and a genotype/phenotype correlation with mutations in the keratin 5 (KRT5) gene is established.

Die zirkumskripte akrale Hypokeratose ist eine seltene, chronische Verhornungsstorung, die bevorzugt bei Frauen beobachtet wird. Die zumeist solitar auftretenden und therapierefraktaren Herde mussen klinisch und histologisch von anderen nicht abheilenden Veranderungen und Tumoren in akraler Haut abgegrenzt werden. Klinisch imponieren die Lasionen als scharf begrenzte erythematose Makulae. Histologisch ist die zirkumskripte akrale Hypokeratose durch einen scharf umschriebenen Verlust der Hornschicht charakterisiert, der sich feingeweblich vor allem in Randbiopsien im Vergleich zur perilasional ortstypisch breiten Hornschicht darstellen lasst.

Panfolliculoma is a rare benign neoplasm showing morphological similarities to the trichogenic trichoblastoma of Headington and the trichoblastoma of Ackerman. Eight patients have been previously reported; we add four additional patients. Their ages ranged from the 2nd to the 6th decade. The neoplasms were primarily situated on the head and the trunk. Clinical examination revealed a skin colored or red, dermal cystic nodule. The histological appearance of the panfolliculoma was characterized by symmetry, sharp circumscription and regular aggregations of cells, which were in parts solid or cystic. Additionally, follicular germs and papillae, matrical, inner and outer rooth sheath differentiation were identified. These varied forms of follicular differentiation were confirmed by the immunohistochemical expression of cytokeratins in different epithelial cells. Panfolliculoma is a benign neoplasm with proven morphological and immunhistochemical follicular differentiation.

Clinical and histopathological findings of 34 cases of desmoplastic malignant melanoma (DMM) are summarized and compared to the literature. DMM develop mostly in sun damaged skin of elderly patients, they are rare and often nonpigmented tumors that are difficult to diagnose clinically. In all cases the tumor parameters showed level IV or V melanomas (level IV: 55.9%, level IV-V: 14.7%, level V: 29.4%) and the tumor thickness measured 3.85 mm +/- 2.31 mm (1.0-11.0 mm). In 22 cases, the follow-up time was between 2 and 7 years. Local recurrences were observed in 7 ( = 31.8%) patients, metastases in 4 ( = 18.2%) and tumor-related deaths in 3. The prognosis for our patients seems to be slightly better than that described in the literature. The main reason is an improved histological diagnosis of this special type of melanoma. Using immunohistochemical staining with anti-S100 antibody it is possible to establish the melanocytic nature of these fibrotic spindle cell tumors earlier that is, in small initial biopsies, and tumor margins can be defined more accurately. As a consequence, surgery is done earlier and is more likely to be curative.

The purpose of this article is to inform about neoplasms with follicular differentiation, particularly trichoblastoma. In 1970 Headington divided neoplasms of the hair germ (trichogenic tumours) into four groups: purely epithelial without inductive changes (trichoblastomas), mixed epithelial-mesenchymal with inductive changes (trichoblastic fibromas), mixed epithelial-mesenchymal with inductive changes and advanced hair follicle formations (trichogenic trichoblastomas), and predominantly mesenchymal with an abortive dermal hair papilla (trichogenic myxoma). Meanwhile a new classification of neoplasms with follicular differentiation has been presented, according to which every neoplasm with follicular differentiation, benign structure (symmetrical, circumscribed, with vertical growth), and predominance of follicular germinative cells is called a trichoblastoma. Whether this neoplasm is malignant and if so to what degree is under discussion. This classification is gaining in acceptance among histopathologists but has not been accepted in the field of clinical dermatology.

On the basis of two cases the differences between the plaque-like variant of dermatofibrosarcoma protuberans (PDFSP) and the plaque-like dermal fibromatosis (synonym: dermatomyofibroma; PDF) are presented. PDFSP and PDF are two clinically very similar dermal fibrous proliferations, but differentiation is important because of their different therapy and prognosis. Histologically and immunohistochemically PDFSP and PDF can be recognized as separate entities.