Spectrum of Melanocytic Proliferation/Differentiation in a Large Series of Cutaneous Neurofibromas: An Under-Recognized Histopathologic Phenomenon and Potential Clue for Neurofibromatosis Type 1

Schwannian and Perineuriomatous Differentiation in a Series of Giant Congenital Melanocytic Nevi

ABSTRACT

Close relationship between melanocytes and neural cells is accepted to reflect their common derivation from the neural crest and tumors combining both elements. We present a series of 10 patients with giant congenital melanocytic nevi (CMN) in which a secondary proliferation (11 lesions) with schwannian and/or perineuriomatous differentiation developed in the course of the disease. The age of the patients (4 male and 6 female) at the time of surgery and histological assessment varied from 3 months to 57 years. Histopathologically, the following subgroups were delineated: (1) nodular/tumoriform "neurotization" in CMN, (2) diffuse neurofibroma-like proliferation within CMN, (3) plexiform neurofibroma-like proliferation within CMN, and (4) diffuse perineuriomatous (hybrid schwannomatous-perineuriomatous) differentiation in CMN. We review the pertinent literature, including the role of recently identified Schwann cell precursors which are believed to represent the nerve-associated state of neural crest-like cells that persists into later developmental stages.

Melanocytic neoplasms in neurofibromatosis type 1: a systematic review

Neurofibromatosis type 1 ( NF1 ) is commonly mutated in melanoma, yet the risk of melanoma in individuals with NF1 is incompletely understood. We performed a systematic review to investigate the risk and characteristics of melanoma and melanocytic nevi in NF1 individuals. PubMed was searched for articles describing NF1 individuals with melanoma, or melanocytic nevi. Those with cutaneous and ocular melanomas were compared to the general population using Surveillance, Epidemiology, and End Results data. Fifty-three articles describing 188 NF1 patients were included (melanoma n  = 82, melanocytic nevi n  = 93, melanocytic nevi, and melanoma n  = 13). Compared to the general population, NF1 patients with cutaneous melanomas had earlier melanoma diagnoses (49.1 vs. 58.6 years, P = 0.012), thicker tumors (3.7 vs. 1.2 mm, P = 0.006), and more frequent disease-specific deaths (27.3% vs. 8.6%, P = 0.005) with shorter survival (12.9 vs. 34.2 months, P = 0.011). Ocular melanomas made up 15.0% of all melanomas in NF1 patients versus 1.5% in the general population ( P < 0.001). In pooling all population-based studies describing melanoma in NF1 populations, NF1 individuals had 2.55 higher odds of having melanoma compared to the general population. A nevus spilus was commonly reported among NF1 individuals with nevi (44.8%, 39/87). Our findings suggest that NF1 individuals may have a higher risk for developing melanomas and tend to have thicker melanomas and worse survival compared to the general population, highlighting the importance of cutaneous and ophthalmologic surveillance in NF1 patients. Our review also supports the association between NF1 and nevus spilus.

Skin anomalies in acromegalic patients (Review of the practical aspects)

Acromegaly is a hormonal disorder which occurs as the result of growth hormone (GH) and insulin growth factor 1 (IGF-1) over-secretion; both hormones are related to skin anomalies. The skin acts as a large endocrine organ, hosting GH receptors in every cell while IGF-1 receptors are expressed only in keratinocytes. This review is a literature review of skin anomalies found in acromegaly, either related to the disease itself or associated with related complications such as secondary diabetes mellitus, or involving associated conditions such as genetic syndromes. The following clinical points are mentioned as follows. Excessive skin and enlargement of soft tissue are due to glycosaminoglycan deposits, edema, and hyperhidrosis (mostly facial and acral). Acanthosis nigricans, a body fold dermatosis associated with insulin resistance, involves local or diffuse hyperkeratotic plaques with or without hyperpigmentation, caused by growth factors including GH/IGF-1. Other findings include cherry angiomas (due to the effects of lipid anomalies on small vessels); oily skin features with keratosis, epidermoid cysts, crochordons, pseudo-acanthosis nigricans; a potentially higher prevalence of varicose veins and psoriasis; low level of evidence for basal cell carcinoma, respective hidroadenitis suppurativa has been noted. In addition, complicated uncontrolled secondary diabetes mellitus (DM) may result in necrobiosis lipoidica diabeticorum, diabetic dermopathy, skin bacterial infections, dermatological complications of diabetic neuropathy, and nephropathy. Finally, associated hereditary syndromes may cause collagenomas, fibromas/angiofibromas, lipomas in multiple endocrine neoplasia type 1 (MEN1) syndrome; café-au-lait macules, early onset neurofibromas, juvenile xanthogranuloma (involving non-Langerhans cell histiocytes), and intertriginous freckling in neurofibromatosis type 1. Clinical findings are differentiated from pseudo-acromegaly such as pachydermoperiostosis. Iatrogenic rash, lipodystrophy (lipoatrophy with/without lipohypertrophy) are rarely reported after pegvisomant/somatostatin analogues or after insulin use for DM. Experiments using human cell lines have shown that GH/IGF-1 over-secretion are prone to epithelial-to-mesenchymal transition (EMT) in melanoma. In non-acromegalic subjects, the exact role of GH/IGF-1 in skin tumorigenesis is yet to be determined. Skin in acromegaly speaks for itself, either as the first step of disease identification or as a complication or part of a complex syndromic context.

Review and update in the diagnosis of peripheral nerve sheath tumors

PURPOSE OF REVIEW

Although tumors with nerve sheath differentiation are vast, the main clinically significant problems faced by the pathologist are the separation of malignant peripheral nerve sheath tumors (MPNSTs) from histologic mimics, the diagnosis of neurofibromatous neoplasms with atypical features, and the separation of cutaneous neurofibromatous neoplasms from melanoma. This review briefly discusses a variety of common nerve sheath tumors and summarizes recent advances on these diagnostic fronts.

RECENT FINDINGS

Much of recent work has focused on abnormalities in polycomb repressive complex 2, and the ways in which these abnormalities may be exploited in the diagnosis of MPNSTs. Progress has been made in the diagnostic and clinical understanding of atypical neurofibromatous neoplasms and low-grade MPNSTs. A number of reports have explored the diagnostic distinction between cutaneous neurofibroma and melanoma.

SUMMARY

New discoveries show promise in the diagnosis of peripheral nerve sheath tumors, but challenges - old and new - remain.