Comparison of the Inflammatory Infiltrates in Tumoral Melanosis, Regressing Nevi, and Regressing Melanoma.

BACKGROUND: Tumoral melanosis (TM) is a histologic diagnosis characterized by abundant pigment-laden macrophages in the dermis. It is generally thought to represent a regressed melanoma, although it has also been reported after benign pigmented lesions as well. Determining the antecedent lesion in cases of TM is of clinical importance to accurately guide therapy and prognostication. Comparing the histopathologic and immunohistochemical (IHC) characteristics of TM, halo nevi (HN), and regressing melanoma (RM) may help predict the antecedent lesion in cases of TM. METHODS: Cases of TM, HN, and RM were selected and assessed for histopathologic (preservation of junctional melanocytic component, depth and width, solar elastosis, fibrosis, and preservation of rete ridge architecture) and IHC (SOX-10, CD138, and PD-1) parameters. PD-L1 immunostaining was also evaluated in cases of HN and RM. RESULTS: Severe solar elastosis, fibrosis, and marked rete ridge effacement were more frequent in RM than in HN. By contrast, numerous plasma cells, clusters of lymphocytes expressing PD-1, and >50% PD-L1 expression in melanocytes were more common in HN than in RM. However, the association of these variables did not reach statistical significance. DISCUSSION: Although studies with higher statistical power are needed, this study serves as an initial investigation to characterize the histopathologic and IHC characteristics, which may help better understand TM and its precursor lesions.

Keratoacanthomatous Changes: Unifying the Histologic Spectrum of Actinic Granuloma.

Actinic granuloma (AG) manifests as annular plaques on sun-damaged skin. There remains no universal consensus on the nosology, etiology, or clinicopathologic criteria of AG as a distinct entity. Broadly, AG is characterized by granulomatous inflammation, multinucleated giant cells, elastophagocytosis, and the absence of mucin and necrobiosis. It is not uncommon, however, to encounter overlapping histological features of other granulomas, such as granuloma annulare and necrobiosis lipoidica, confounding the diagnosis of this controversial entity. Herein, we describe 2 cases of AG with features of granuloma annulare and necrobiosis lipoidica, supporting the concept of AG as a histologic spectrum. These 2 cases displayed dilated follicular infundibula and pseudoepitheliomatous hyperplasia analogous to changes in keratoacanthomas. These unique epithelial changes, in tandem with characteristic elastin alterations and clinical findings, are helpful and unifying features that permit accurate diagnosis of this controversial entity.

Langerhans Cell Histiocytosis With Clinical and Histologic Features of Hidradenitis Suppurativa: Brief Report and Review.

Langerhans cell histiocytosis (LCH) is an uncommon histiocytic disorder in adults. Clinically, this rare entity can mimic other dermatologic conditions, including hidradenitis suppurativa. A case of LCH is reported with clinical and histologic features of hidradenitis suppurativa, along with a review of these unusual findings. Clinical dermatologists and dermatopathologists benefit from awareness of this unique presentation, which may prompt earlier identification and diagnosis of adult patients with LCH.