Dermatopathologic features of cutaneous squamous cell carcinoma and actinic keratosis: Consensus criteria and proposed reporting guidelines.

BACKGROUND: There is considerable variation in the literature regarding the dermatopathologic diagnostic features of and reporting guidelines for actinic keratosis (AK) and cutaneous squamous cell carcinoma (cSCC). OBJECTIVE: To develop consensus recommendations regarding diagnostic criteria, nomenclature, and reporting of AK and cSCC. METHODS: Literature review and cross-sectional multiround Delphi process including an international group of expert dermatopathologists followed by a consensus meeting. RESULTS: Consensus was achieved regarding the key dermatopathologic features necessary for diagnosing cSCC, AK, and associated variants; grading of degree of cellular differentiation in cSCC; utility of immunohistochemistry for diagnosis of cSCC; and pathologic features that should be reported for cSCC and AK. LIMITATIONS: Consensus was not achieved on all questions considered. CONCLUSION: Despite the lack of clarity in the literature, there is consensus among expert dermatopathologists regarding diagnostic criteria and appropriate reporting of AK and cSCC. Widespread implementation of these consensus recommendations may improve communication between dermatopathologists and clinicians, facilitating appropriate treatment of AK and cSCC.

False-Negative Rate of Direct Immunofluorescence on Lower Extremities in Bullous Pemphigoid.

ABSTRACT: Bullous pemphigoid (BP) is the most common autoimmune blistering disorder of the skin. It is typified by tense blisters with a subepidermal split and mixed dermal inflammatory infiltrate on histology. Biopsy of the perilesional skin for direct immunofluorescence (DIF) has become the gold standard in the diagnosis of BP. Currently there is a pervasive clinical opinion that the lower extremity is a site with a high false-negative rate (FNR) for DIF in the diagnosis of BP. This notion is primarily based on 2 early studies from the 1980s without more recent confirmatory studies. To readdress this question regarding the lower extremities, a retrospective study from 2012 to 2018 was performed in our institution that evaluated the FNR of DIF by an anatomical site in the diagnosis of BP. Cases of BP were identified using standard criteria (clinical and histological data reviewed in cases with negative DIF), and overall, 79 patients were included in the study. A total of 4 false-negative DIF biopsies were verified. Two negative DIF were from the lower extremity yielding a FNR of 10% compared with 4% on the trunk and 3% from the upper extremity, with no statistically significant difference by anatomical sites. Our study fails to demonstrate a high FNR of DIF from the lower extremity in the diagnosis of BP.

Syringotropic Mycosis Fungoides: A Variant of Folliculotropic Mycosis Fungoides or a Distinct Entity?

Syringotropic mycosis fungoides (MF) is classified under folliculotropic MF. Although there is significant overlap between the 2, this study demonstrates that folliculotropism is frequently present in syringotropic MF, and when not present, the specimen did not include a follicle to examine. In addition, few of the pathology reports mentioned folliculotropism or syringotropism, although this is an important prognostic feature.

"Low-Fat" Pseudoangiomatous Spindle Cell Lipoma: A Rare Variant With Loss of 13q14 Region.

Spindle cell and pleomorphic lipoma constitute a spectrum of lipomatous lesions with characteristic clinical, morphologic, immunohistochemical, and molecular features. Multiple variants have been previously described including vascular, fibrous, plexiform, and those with significantly less fat termed "low-fat" and "fat-free" by Folpe. Cytogenetically, spindle cell lipomas frequently display monoallelic loss of 13q14 region, an abnormality also found in cellular angiofibroma and mammary-type myofibroblastoma. Pseudoangiomatous spindle cell lipoma, originally described by Fletcher et al in 1994, is a rare variant within the spindle cell/pleomorphic lipoma spectrum, with less than 20 published cases. It consists of an admixture of spindle cells, "ropey" collagen, variable amounts of mature fat, and irregular, branching slit-like vascular spaces. The authors present a case of a 1-cm subcutaneous lesion excised from the neck of a 70-year-old man with classic histologic and immunohistochemical features of "low-fat" pseudoangiomatous spindle cell lipoma. Fluorescence in situ hybridization demonstrated a loss of 13q14 region, a characteristic presumed cytogenetic finding of spindle cell lipoma, which has been previously unconfirmed in this variant.

Keratoacanthoma clinical behavior: a systematic review.

As of 2013, keratoacanthomas (KAs) have not been decided on as either a benign or a malignant entity. Originally considered benign epidermal growths, the assertion by Hodak, Jones, and Ackerman that these lesions are truly "an expression of squamous cell carcinoma" (SCC) fueled the controversy and placed some of the biggest names in the field on opposite sides of the issue. Without a clear understanding of the etiology of KAs and without stringent diagnostic criteria, the literature in regard to KA contains scant reports of their "metastatic potential." Four hundred forty-five cases of KA with reported follow-up and outcomes were reviewed from 113 published articles. In our data set, none of these cases resulted in death or distant metastases. When compared with 429 cases of SCC of the skin, with 61 cases of metastases and 24 deaths as a direct result of SCC, the biologic behavior of the 2 entities is distinct and evident. KAs are benign epidermal growths and not a malignant variant of SCC.

Multiple myeloma diagnosed secondary to analysis of a lytic bone lesion encountered during Mohs micrographic surgery.

An 89-year-old man underwent Mohs micrographic surgery for treatment of a squamous cell carcinoma of the scalp. A lytic bone lesion was found that led to the diagnosis of multiple myeloma.

Histologic features of scalp melanocytic nevi.

BACKGROUND: The scalp has been proposed as an anatomic site that harbors melanocytic nevi with distinctive histologic attributes, so-called "special-site" nevi, similar to nevi on the breast and genitalia. However, detailed studies are lacking. OBJECTIVE: We sought to better delineate the features of scalp melanocytic nevi, particularly lesions that may qualify as special-site nevi. METHODS: The histologic features of 365 total melanocytic nevi of the scalp were studied from 322 patients over a consecutive period of 18 months from July 2007 through January 2009. RESULTS: A total of 56 nevi with characteristic features were identified. The most common features were: (1) random melanocytes containing large nuclei (92.9%) and abundant pale cytoplasm with dusty melanin granules (96.4%); (2) large nests (76.8%) situated along the sides of rete and between rete ridges (85.7%); (3) nests of poorly cohesive melanocytes (82.1%); (4) overlap features with Clark nevi (75.0%); and (5) overlap features with superficial congenital nevi (50.0%). Pagetoid spread (14.3%), asymmetry (23.2%), and poor lateral demarcation (16.1%) were less common. These 56 lesions predominated in the first 2 decades of life and were not observed after age 35 years. LIMITATIONS: Lack of long-term clinical follow-up of patients is a limitation; however, no recurrences or malignancies from these patients' scalps were submitted in the time period (≥ 3 years) since the initial biopsies. CONCLUSION: A special site scalp nevus is recognizable amongst scalp melanocytic nevi, and this lesion is more common in younger patients. Familiarization of its features should assist in the diagnosis and management of scalp melanocytic lesions.

Molecular biology of melanoma.

Dermatologists and dermatopathologists face the difficulties of accurately diagnosing and treating atypical melanocytic lesions and melanomas. Despite huge advances in medicine, our management of melanoma has not significantly changed in many years. The biggest gains made recently have been in the identification of common mutations in melanoma and the use of these mutations to aid in the diagnosis and treatment of melanoma. To understand these gains one must first be familiar with the regulatory pathways of melanoma and the most common mutations found there. This article will review the function and significance of the most studied mutations in melanoma and briefly discuss new and planned treatment options.

Giant fibrous hamartoma of infancy: a report of two cases and review of the literature.

We present two unique cases of fibrous hamartoma of infancy defined by giant-sized and/or multicentric cutaneous and subcuticular lesions--features not, to our knowledge, reported to coexist. We review the nature of such tumors and examine the clinical implications of tumor size and multicentricity on risk for recurrence and likelihood of visceral involvement.