"Puffy shirt appearance": Cell crowding at low magnification may represent nevoid melanoma

Unusual conjunctival melanocytic proliferations. Report of five cases and review of the literature

Indeterminate melanocytic proliferations of the conjunctiva have both benign and malignant features that previously made these lesions nearly impossible to categorize in existing classification schemes. With the evolution of immunohistochemistry and molecular genetics, however, subclassifications have emerged that allow for a more tailored diagnosis and management. These conjunctival melanocytic proliferations include deep penetrating nevus, granular cell nevus, and nevoid melanoma. There remains a small subset of conjunctival melanocytic proliferations that defy precise characterization as nevi, primary acquired melanosis, or melanomas despite currently available ancillary diagnostic modalities and remain indeterminate. We highlight these unusual types of nevi and melanomas, with an update on their morphologic, immunohistochemical, and molecular genetic characteristics.

Cognitive bias in pathology, as exemplified in dermatopathology

Cognitive bias refers to human thinking patterns, as well as pitfalls, that are reproducible. Importantly, cognitive bias is not intentionally discriminatory and is necessary to properly interpret the world around us, including microscopic slides. Thus, it is a useful exercise to examine cognitive bias in pathology, as exemplified in dermatopathology.

Dermoscopic features of nevoid melanoma: a retrospective study

BACKGROUND

Nevoid melanoma (NeM) is a rare variant of melanoma resembling melanocytic nevus. The aim of the study was to systematically review the dermoscopic features of NeM.

METHODS

A hospital-based retrospective study was conducted. Dermoscopic features of NeMs diagnosed through excisional biopsy between January 2015 1, and March 1, 2021, were compared to superficial spreading melanomas (SSMs) matched by Breslow's thickness. Then, a literature search was performed. Electronic searches on PubMed database via Medline were conducted to retrieve any manuscript reporting detailed dermoscopic features of histopathologically confirmed NeM.

RESULTS

A total of 60 malignant melanomas (MM) comprising 20 NeM and 40 SSM were collected. Twelve out of 20 (60%) NeM showed a nevus-like appearance, including reticular and globular patterns, and in 35% of these cases it was detected because of dermoscopic changes. Then, a total of seven original manuscripts were retrieved from the literature review, comprising 56 cases overall. NeM showed nevus-like pattern in 53% of the cases, multicomponent pattern in 21% and amelanotic in 9%. Enlargement, irregularly distributed dots/globules, irregular pigmentation, and atypical vascular pattern were found in NeM with nevus-like appearance. NeM with multicomponent pattern were characterized by irregular pigmentation, blue-white veil, irregular dots and atypical vascular pattern. Amelanotic NeM is rare and show atypical vascular pattern and milia-like cysts.

CONCLUSIONS

Dermoscopy of NeM is challenging as it frequently shows a nevus-like pattern, but clues and detection of dermoscopic changes may help to identify it.

Cutaneous Melanomas Arising during Childhood: An Overview of the Main Entities

Cutaneous melanomas are exceptional in children and represent a variety of clinical situations, each with a different prognosis. In congenital nevi, the risk of transformation is correlated with the size of the nevus. The most frequent type is lateral transformation, extremely rare before puberty, reminiscent of a superficial spreading melanoma (SSM) ex-nevus. Deep nodular transformation is much rarer, can occur before puberty, and must be distinguished from benign proliferative nodules. Superficial spreading melanoma can also arise within small nevi, which were not visible at birth, usually after puberty, and can reveal a cancer predisposition syndrome (CDKN2A or CDK4 germline mutations). Prognosis is correlated with classical histoprognostic features (mainly Breslow thickness). Spitz tumors are frequent in adolescents and encompass benign (Spitz nevus), intermediate (atypical Spitz tumor), and malignant forms (malignant Spitz tumor). The whole spectrum is characterized by specific morphology with spindled and epithelioid cells, genetic features, and an overall favorable outcome even if a regional lymph node is involved. Nevoid melanomas are rare and difficult to diagnose clinically and histologically. They can arise in late adolescence. Their prognosis is currently not very well ascertained. A small group of melanomas remains unclassified after histological and molecular assessment.

Histopathologic classification and prognostic factors of melanoma: a 2021 update

Despite the rapid recent advances in molecular analysis of tumors, which allow large-scale and high-resolution genomics, the "gold standard" for melanoma diagnosis continues to be histopathology, in conjunction with clinical characteristics and sometimes with important support of immunohistochemistry. Observations, where postulated that cutaneous melanomas may arise through two distinct pathways, discoveries such as that BRAF^V600E mutations were mostly common in melanomas on sun-exposed skin with little solar elastosis and seminal works for melanoma progression and evolution set the groundwork for the new WHO Classification of Melanoma: a classification of melanoma that not only encompasses histologic but also clinical, epidemiologic, and genetic characteristics. The melanomas were divided into those etiologically related to sun exposure and those that are not, based on their mutational signatures, anatomic site, and epidemiology. On the basis of degree of associated solar elastosis melanomas on the sun exposed skin were further divided by the histopathologic degree of cumulative solar damage (CSD) of the surrounding skin, into low and high CSD. On the low-CSD group of melanomas are included superficial spreading melanomas, while the high-CSD melanomas encompasses lentigo maligna and desmoplastic melanomas. The "non-CSD" classification includes acral melanomas, some melanomas in congenital nevi, melanomas in blue nevi, Spitz melanomas, mucosal melanomas, and uveal melanomas. Nodular and nevoid melanoma may occur in any pathway. A group of intermediate tumors termed melanocytoma is proposed for tumors that in addition to mutations that activate the MAPK pathway, harbor multiple driver mutations, and they are either low-grade or high-grade, to indicate that they may carry a higher risk of malignant transformation. In this review a summary of the most recent WHO classification of melanoma is provided. A short analysis of essential histopathologic prognostic parameters is also provided. The new classification of melanoma discriminates distinct types of melanoma based on their clinicopathologic, and genomic characteristics. Undoubtedly, melanoma research will continue to evolve as new clinical, pathological, molecular data accumulates. The challenge of the forthcoming years is to better characterize the intermediate category of melanocytic lesions.