Search

Abstract: Cutaneous mastocytosis is characterized by the abnormal accumulation of mast cells in the skin. However, mast cell counting is not always easy and reproducible with classical methods. This work aims to demonstrate the reliability, usability, and virtues of a new software used on digital tablets for counting mast cells in cutaneous specific lesions of mastocytosis, to assess differences in mast cell counts between clinical subtypes of mastocytosis in the skin, and to consider the feasibility of applying a diagnostic mast cell count cutoff to urticaria pigmentosa, which is the most frequent form of cutaneous mastocytosis. Using a new digital tablet software that was accessible by multiple observers through its own wireless network and allowed high resolution of the image without data compression, we counted the number of mast cells on slides of patients and control skins immunostained for CD117. We found that our counting method was highly reproducible and that the new software allowed very quick counting. We evidenced strong differences in the mast cell count between most of the clinical subtypes of mastocytosis in the skin. However, when applied to a subset of patients with urticaria pigmentosa, a diagnostic cutoff in the mast cell count lacked sensitivity. Thus, our digital method for counting CD117-immunostained mast cells was highly accurate and was of a significant value for the diagnosis of mastocytosis in the skin. However, some subtypes with low mast cell counts will still require the application of additional diagnostic criteria., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Introduction: Pityriasis lichenoides (PL) is an infrequent skin disorder. The clinical manifestations are usually specific enough for a reliable diagnosis, although the histopathological assessment of a biopsy is sometimes needed to differentiate between PL and a range of other diseases. The objectives of this study were to review cases of PL managed in our hospital, confirm the classical histopathological features of PL, and identify signs that may be of value in the diagnosis of PL., Materials and Methods: All cases of PL assessed in our pathology department between January 2007 and December 2017 were retrieved, and all slides were reviewed. Cases were selected only if a diagnosis of PL was initially suggested by a dermatologist and then confirmed by the histopathological assessment., Results: Seventy-one cases met the study criteria. The following features were almost always present: vacuolar changes or necrotic keratinocytes (100%), both superficial and deep lymphocytic infiltrates (99%), and the infiltration of lymphocytes into the adnexal epithelium (97%). The inflammatory cells were always small- to medium-sized lymphocytes. There were no eosinophilic infiltrates. Superficial perivascular and/or intraepidermal red blood cells were observed in 83% of cases., Discussion: We highlighted the presence of a deep dermal lymphocytic infiltrate, with a "T-shaped" periadnexal arrangement along the full length of the follicular and sudoral epithelia. This might be a feature that enables the differentiation of PL from other diseases. Our findings also prompted a number of physiopathological hypotheses for PL., Conclusions: Our present results confirmed the classical histological aspects of PL and provided some useful new diagnostic features.

Langerhans cell (LC) histiocytoma is a neonatal tumor that often consists of a single, ulcerated nodule. Systemic involvement is rare, and LC histiocytoma is considered to be a variant of congenital, self-healing LC histiocytosis (also referred to as Hashimoto-Pritzker disease). In view of its low prevalence, LC histiocytoma is not always diagnosed in a clinical examination and requires histological confirmation. Furthermore, the histological and molecular features of LC histiocytoma have not been well characterized. Here, we report on 6 cases of this rare disease and review the corresponding literature. LC histiocytoma differs from classical self-healing LC histiocytosis with regard to the pathological features; we found that LC histiocytoma was associated with massive infiltration by histiocytes of various sizes and shapes (although often large) throughout the dermis and the superficial subcutis. Epidermotropism was rare, mitotic figures were not inconspicuous, and necrotic or calcified areas were often present. Immunohistochemical assessment revealed a mixture of different types of histiocytes (with CD1a CD207, CD1a CD207, and CD1a CD207 CD163 cells). Genetic testing was performed in 5 cases; it revealed a BRAF mutation (p.V600E and p.485_490delinsF) in 2 cases, a HRAS mutation (p.T58I) in 1 case, a combination of 2 PTEN mutations in another case (p.I224M and p. R234W), and no mutations in the fifth case. All the lesions regressed spontaneously, and none recurred during follow-up.

Netherton syndrome (NS) is a severe genetic skin disorder, with often delayed or misleading clinical signs. The histological features of skin biopsies, usually described as a psoriasiform hyperplasia, have only been reported in isolated case reports or small case series. The aim of this study is to define, for the first time, the precise histological pattern of cutaneous lesions, in a large cohort of skin biopsies from confirmed NS patients. The study included 80 consecutive skin biopsies from 67 patients taken between January 1995 and June 2014. All were from confirmed NS patients with either a negative lympho-epithelial Kazal-type-related inhibitor (LEKTI) immunohistochemistry and/or molecular confirmation by identified mutation in SPINK5. In this cohort, the most frequent histological finding was also psoriasiform hyperplasia, but there were additional, less common, or previously unreported findings, including compact parakeratosis with large nuclei, subcorneum or intracorneum splitting, presence of clear cells in the upper epidermis or stratum corneum, dyskeratosis, dermal infiltrate with neutrophils and/or eosinophils, and dilated blood vessels in the superficial dermis. An early confirmation of the diagnosis of NS is essential for improved patient management. Thus, in the situation of a patient with an unknown skin disorder and non specific clinical presentation, the dermatopathologist may now be able to suggest the diagnosis of NS based on these newly reported characteristics. However, LEKTI immunohistochemistry remains the essential diagnostic investigation in cases with misleading or nonspecific histological features and is mandatory for the definitive diagnosis of NS in all patients.