What's New in Dermatopathology: Inflammatory Dermatoses.

Inflammatory skin diseases encompass a vast array of conditions. The field continues to expand and evolve with resurgence of conditions, through newly recognized medication adverse effects, and via more detailed descriptions of known dermatoses. The importance of clinicopathologic correlation and an up to date knowledge of dermatologic conditions cannot be overstated. This review focuses on an array of recent important developments in the histologic diagnosis of inflammatory conditions that affect the skin.

p53 Is a Helpful Marker in Distinguishing Langerhans Cell Histiocytosis From Langerhans Cell Hyperplasia.

Langerhans cell histiocytosis (LCH) is a proliferative disorder of Langerhans cells that can be challenging to distinguish histologically from Langerhans cell (LC) hyperplasia, seen in a variety of inflammatory dermatoses. Lesional cells in both entities demonstrate positive staining for CD1a and S100. Previous studies have demonstrated positive staining of fascin, CD31, and p53 in cases of LCH, but currently, no studies have compared the staining profiles of these markers between LCH and LC hyperplasia. The authors compared immunohistochemical staining profiles of LCH (n = 15) and various inflammatory dermatoses with LC hyperplasia (n = 15) using fascin, CD31, and p53. Fascin, CD31, and p53 were graded as a percentage of CD1a staining cells in the epidermis and dermis of each specimen. Fascin showed no significant differences in staining between the 2 entities. CD31 was positive in the dermal infiltrate in 40% of cases of LCH and negative in all cases of LC hyperplasia. p53 was positive in the epidermal infiltrate in 50% of cases of LCH, and positive in the dermal infiltrate in 93% of cases of LCH, whereas negative in all cases of LC hyperplasia. Fascin was not a helpful marker in distinguishing LCH from LC hyperplasia. CD31, if positive in the dermal infiltrate, is suggestive of a diagnosis of LCH, but exhibits a relatively low sensitivity for this purpose. p53 proved to be a helpful and accurate diagnostic immunohistochemical stain when distinguishing between LCH and LC hyperplasia.

Clinical Practice Guidelines for Cutaneous Lymphomas.

Primary cutaneous lymphomas are non-Hodgkin lymphomas, which are broadly divided into cutaneous T-cell lymphomas and cutaneous B-cell lymphomas. These classifications include numerous distinct entities, all with varying clinical presentations and disease courses. Herein, we will review the cutaneous T-cell lymphomas, including Mycosis Fungoides, Sézary syndrome, CD30+ lymphoproliferative disorders, as well as other less common entities. Cutaneous B-cell lymphomas will also be discussed, including primary cutaneous marginal zoned lymphoma, cutaneous follicle-center lymphoma, diffuse large B-cell lymphoma, leg type, as well as other less common entities. Accurate and early diagnosis is key, as the treatment and prognosis varies significantly between conditions.

Cavernous hemangioma-like Kaposi sarcoma: a unique histopathologic variant.

Kaposi sarcoma (KS) is an angiolymphatic neoplasm with multifactorial etiology. Clinically, KS has been divided into 4 distinct types and 3 well-defined histologic stages. Rare reports in the literature have characterized additional unique histopathologic variants. The authors report a case of KS, confirmed with human herpesvirus type 8 and D2-40 staining, which resembled a cavernous hemangioma on histopathology.

Crohn's disease presenting as a neutrophilic dermatosis in a 5-month-old boy.

A 5-month-old boy with a previous history of failure to thrive and poor feeding was admitted to the hospital with failure to thrive, oral ulcers, and a generalized vesiculopustular rash that demonstrated a subcorneal pustule and neutrophilic infiltrate on histology. Esophagogastroduodenoscopy and flexible sigmoidoscopy biopsies demonstrated chronic active colitis with granulomas, consistent with the diagnosis of Crohn's disease. Our case represents, to our knowledge, the youngest person reported with this condition in association with Crohn's disease.

Presence of Mast Cells and Mast Cell Degranulation in Scalp Biopsies of Telogen Effluvium.

BACKGROUND: Telogen effluvium (TE) is a type of acquired, diffuse alopecia that occurs due to an abnormal shift of scalp hair follicles from anagen to telogen, leading to premature shedding of hair. Previous studies have suggested the existence of a neuroimmunologic "brain-hair follicle" axis, in which mast cells have been implicated as an important link between the nervous system and immunologic system. OBJECTIVE: The current study sought to investigate the role of mast cell presence and mast cell degranulation in the pathogenesis of TE. MATERIALS AND METHODS: Mast cells were counted using Giemsa and tryptase immunohistochemical stains in scalp biopsy specimens with the pathologic diagnosis of TE (TE, n = 10), alopecia areata (AA, n = 7), and androgenic alopecia (ANDRO, n = 9). RESULTS: We found significant (P < 0.001) group-level differences between the mean mast cell counts per high-power fields for each type of alopecia studied. Tukey post hoc analysis showed the mean mast cell count for TE to be significantly larger than AA for both Giemsa (P = 0.002) and tryptase (P = 0.006); significantly larger than ANDRO for both Giemsa (P < 0.001) and tryptase (P < 0.001); and significantly larger when compared to normal scalp skin for both Giemsa (P < 0.001) and tryptase (P < 0.001). No significant difference of mean mast cell counts was observed for AA compared to ANDRO for Giemsa (P = 0.373) or tryptase (P = 0.598) stains. CONCLUSION: Our findings suggest that mast cells could play a role in mediating stress-induced hair loss seen in TE.