Congenital melanocytic nevi with placental infiltration by melanocytes: a benign condition that mimics metastatic melanoma

Neurocutaneous melanocytosis (melanosis)

Neurocutaneous melanosis (NCM; MIM # 249400; ORPHA: 2481], first reported by the Bohemian pathologist Rokitansky in 1861, and now more precisely defined as neurocutaneous melanocytosis, is a rare, congenital syndrome characterised by the association of (1) congenital melanocytic nevi (CMN) of the skin with overlying hypertrichosis, presenting as (a) large (LCMN) or giant and/or multiple (MCMN) melanocytic lesions (or both; sometimes associated with smaller "satellite" nevi) or (b) as proliferative melanocytic nodules; and (2) melanocytosis (with infiltration) of the brain parenchyma and/or leptomeninges. CMN of the skin and leptomeningeal/nervous system infiltration are usually benign, more rarely may progress to melanoma or non-malignant melanosis of the brain. Approximately 12% of individuals with LCMN will develop NCM: wide extension and/or dorsal axial distribution of LCMN increases the risk of NCM. The CMN are recognised at birth and are distributed over the skin according to 6 or more patterns (6B patterns) in line with the archetypical patterns of distribution of mosaic skin disorders. Neurological manifestations can appear acutely in infancy, or more frequently later in childhood or adult life, and include signs/symptoms of intracranial hypertension, seizures/epilepsy, cranial nerve palsies, motor/sensory deficits, cognitive/behavioural abnormalities, sleep cycle anomalies, and eventually neurological deterioration. NMC patients may be symptomatic or asymptomatic, with or without evidence of the typical nervous system changes at MRI. Associated brain and spinal cord malformations include the Dandy-Walker malformation (DWM) complex, hemimegalencephaly, cortical dysplasia, arachnoid cysts, Chiari I and II malformations, syringomyelia, meningoceles, occult spinal dysraphism, and CNS lipoma/lipomatosis. There is no systemic involvement, or only rarely. Pathogenically, single postzygotic mutations in the NRAS (neuroblastoma RAS viral oncogene homologue; MIM # 164790; at 1p13.2) proto-oncogene explain the occurrence of single/multiple CMNs and melanocytic and non-melanocytic nervous system lesions in NCM: these disrupt the RAS/ERK/mTOR/PI3K/akt pathways. Diagnostic/surveillance work-ups require physical examination, ophthalmoscopy, brain/spinal cord magnetic resonance imaging (MRI) and angiography (MRA), positron emission tomography (PET), and video-EEG and IQ testing. Treatment strategies include laser therapy, chemical peeling, dermabrasion, and surgical removal/grafting for CMNs and shunt surgery and surgical removal/chemo/radiotherapy for CNS lesions. Biologically targeted therapies tailored (a) BRAF/MEK in NCM mice (MEK162) and GCMN (trametinib); (b) PI3K/mTOR (omipalisib/GSK2126458) in NMC cells; (c) RAS/MEK (vemurafenib and trametinib) in LCMNs cells; or created experimental NMC cells (YP-MEL).

Uterine inflammatory myofibroblastic tumors in pregnant women with and without involvement of the placenta: a study of 6 cases with identification of a novel TIMP3-RET fusion

Uterine inflammatory myofibroblastic tumors (IMTs) have been reported in association with pregnancy and, in some instances, secondarily involve the placenta. The clinicopathological spectrum of these tumors in the setting of pregnancy is not well defined. We investigated the clinical, morphologic, immunohistochemical, molecular cytogenetic, and genetic features of 6 uterine IMTs occurring in pregnant women. Each tumor was discovered at parturition, and none was identified by prenatal ultrasound. Patient age ranged from 25 to 41 years (mean 31.5). Tumor size ranged from 1.5 to 9 cm (mean 4.7). Four of 6 had usual IMT features, with at least focal deciduoid change in 3. Necrosis was identified in 3 tumors; and multinucleated cells, in 3 tumors. Sex hormone receptor expression was consistent with estrogen receptor negative or focally weakly positive and progesterone receptor diffusely moderately or moderately to strongly positive in all 6 tumors. ALK immunohistochemistry was strongly positive in 5 tumors, and all of these had an ALK rearrangement detected by break-apart fluorescence in situ hybridization. Subsequent RNA sequencing of these 5 tumors identified a TIMP3-ALK fusion in 4 and a THBS1-ALK in 1. In the ALK-negative tumor, RNA sequencing detected a novel TIMP3-RET fusion that was confirmed by RET break-apart fluorescence in situ hybridization. Follow-up was available for 2 of 6 patients 5 and 19 months after diagnosis. Neither patient developed recurrence. ALK immunohistochemistry will distinguish most uterine IMTs, but if ALK expression and gene studies are negative, in the appropriate morphologic context, evaluation of other tyrosine kinase genes known to be more commonly altered in extrauterine IMTs such as ROS1, NTRK3, PDGFRβ, and RET may be necessary for diagnostic confirmation.

Pathology and genomics of pediatric melanoma: A critical reexamination and new insights

The clinicopathologic features of pediatric melanoma are distinct from those of the adult counterpart. For example, most childhood melanomas exhibit a uniquely favorable biologic behavior, save for those arising in large/giant congenital nevi. Recent studies suggest that the characteristically favorable biologic behavior of childhood melanoma may be related to extreme telomere shortening and dysfunction in the cancer cells. Herein, we review the genomic profiles that have been defined for the different subtypes of pediatric melanoma and particularly emphasize the potential prognostic value of telomerase reverse transcriptase alterations for these tumors.

Amplification of mutated NRAS leading to congenital melanoma in neurocutaneous melanocytosis

The mechanisms behind malignant progression in patients with giant nevi are largely unknown. Here, we aim to describe novel genetic findings and explain possible mechanisms resulting in the most severe form of neurocutaneous melanocytosis. Detailed histological (biopsy and post-mortem) studies, tissue culture, and high-resolution cytogenetic analysis, including chromosome and array comparative genomic hybridization, Ion AmpliSeq Cancer Panel, and Sanger sequencing, were performed on tissues from a white male who succumbed at 17 months of age to congenital melanoma associated with a bathing-trunk nevus. We also used quantitative PCR to quantitatively assess the expression of NRAS among normal cells, including fibroblast and melanocytes, as well as melanoma cells from our patient. Full autopsy documented tumors in the brain, spinal cord, lung, liver, testis, bone marrow, and, retrospectively, in the placenta. Next-generation sequencing and chromosome microarray in our patient revealed novel findings, including duplication of a mutated NRAS gene, leading to an aggressive clinical course and disseminated disease. Quantitative PCR showed a five-fold increase in NRAS expression in the melanoma cell line when compared with normal melanocytes. Finally, three amino acid-changing germline variants were detected: homozygous TP53 p.P72R, heterozygous KIT p.M541L, and homozygous KDR (VEGFR2) p.Q472H. These genes are involved in malignancy and other potentially relevant pathways, such as mast cell and melanocytic signaling, as well as angiogenesis. These findings provide novel insights into the biology of congenital melanocytic proliferations, showing that amplification of mutated NRAS seems to represent a new genetic mechanism leading to melanoma in the context of neurocutaneous melanocytosis.

Pseudotumors of the placenta

The placenta is one of the most common gross pathology specimens encountered by surgical pathologists, yet primary tumors are exceptionally rare and even rarer are entities with the potential to mimic malignancy. There are many nonneoplasticmass forming lesions in the placenta that are important to be aware of as many of these can be associated with adverse outcomes in the mother and fetus. Also important are entities which may be observed microscopically in the placenta and potentially confused as a malignancy. Knowledge of these potential pitfalls is essential to avoid making an incorrect diagnosis and causing undue alarm.

Congenital nevi versus metastatic melanoma in a newborn to a mother with malignant melanoma - diagnosis supported by sex chromosome analysis and Imaging Mass Spectrometry

A 37-year-old pregnant woman presented with a 2-cm irregular reddish nodule on her left upper arm during pregnancy. A biopsy from the lesion showed a 2.2-mm thick malignant melanoma with intravascular invasion, 25 mitosis/mm(2) and no ulceration. Following induction of labor, the patient underwent re-excision with sentinel lymph node biopsy. This showed no residual melanoma and no lymph node metastasis. The newborn boy had multiple pigmented lesions on the trunk, some of which were large and irregular. Two were biopsied and histologic examination showed dense dermal proliferation of medium sized melanocytes with multiple mitotic figures and no maturation with their descent into the dermis, raising suspicion of transplacental metastases. Examination of the placenta failed to show metastatic lesions. Multiplex polymerase chain reaction (PCR)-based genotyping, including testing for amelogenin locus for sex chromosome determination, demonstrated the presence of Y chromosome material in the melanocytes of the newborn's lesions excluding maternal origin. A diagnosis of congenital nevi was rendered. Subsequently, Imaging Mass Spectrometric analysis of the mother's lesion showed proteomic signature expression indicative of malignant melanoma, whereas the two lesions in the newborn showed changes indicative of nevi. This case demonstrates the utility of genotyping and Mass Spectrometry analysis in this challenging clinical scenario.

Neurocutaneous melanocytosis

Neurocutaneous melanosis or neurocutaneous melanocytosis is a rare sporadic congenital disorder characterized by the presence of giant and/or multiple satellite congenital melanocytic nevi in the skin and benign melanocytic pigmentation of the leptomeninges. These two defining features were recognized more than a century ago. A third characteristic feature is proliferative nodules arising from giant nevi. The etiology is unknown, but neurocutaneous melanosis is considered a developmental disorder of melanocyte precursors from neural crest. The distinctive unique distribution of the congenital giant nevi that gives a "garment" appearance is also an expression of the neural crest. The neurological manifestations often appear in infancy.The special association of neurocutaneous melanosis with Dandy-Walker malformation complex may be explained by a common pathogenesis. Mortality in infancy and childhood is high.

Angiotropic neonatal congenital melanocytic nevus: how extravascular migration of melanocytes may explain the development of congenital nevi

In the following report we describe a medium-sized congenital melanocytic nevus (CMN) on the upper back of a female patient biopsied at 9 days of age. This case is a unique variant of CMN occurring in the neonatal period that mimics malignant melanoma. This is not only because of histologic features such as a large round or ovoid cellular phenotype of melanocytes mimicking melanoma cells but also because of conspicuous angiotropism, a finding not previously reported in such CMN. Immunostaining for blood and lymphatic vessels demonstrated angiotropism of melanocytes about blood vessels but not lymphatics. We have already emphasized the significance of angiotropism as a marker of extravascular migratory metastasis (EVMM) of melanoma. EVMM, a process by which tumor cells migrate along vessels and other tracks, has striking parallels with the migration of embryonic stem cells from the neural crest. Thus we propose, because angiotropism is a common finding in CMN and metastatic melanoma, that (1) such pathways of cellular migration may result in the genesis of CMN and other melanocytic neoplasms; and (2) the dysregulation of such embryonic pathways may result in the retrograde migratory phenomena of melanoma as already described. In summary, extravascular cellular migration of melanocytes seems to be fundamental for melanoma (perhaps other cancer) metastasis but also hypothetically may be important for the development of other melanocytic lesions such as CMN and requires further investigation.

Familial clustering of giant congenital melanocytic nevi

Giant congenital melanocytic nevus (GCMN) is an infrequently occurring congenital malformation. GCMN generally occurs in isolation but rare familial occurrence points to a genetic background. We present two cases of familial GCMN: one with two affected siblings and another with two affected double second cousins. Familial occurrence of GCMN reported in literature is reviewed and an overview of the embryology and proliferation given, illustrating the plethora of factors that might lead to GCMN formation. The pattern of inheritance is likely not Mendelian and discordance in identical twins and the segmental distribution of lesions suggest a post-zygotic mutation. A polygenic paradominant inheritance best explains the clinically observed transmission pattern. Candidate genes include those influencing neural crest development and melanocyte proliferation.

Neurocutaneous melanosis in association with encephalocraniocutaneous lipomatosis

We describe a white female infant with neurocutaneous melanosis (NCM) and encephalocraniocutaneous lipomatosis (ECCL). Multiple, giant and small congenital melanocytic nevi (CMN) were observed on the head, neck and trunk and involved 70% of body surface area. Histologic examination of several CMN revealed atypical nodular proliferations of dermal nevomelanocytes. In a small (<1 cm) truncal CMN, single and dyscohesive intraepidermal nests of atypical nevomelanocytes simulating a superficial spreading melanoma, were observed. The placenta was grossly normal and histologically demonstrated multiple banal appearing nevomelanocytes within the stroma of its villi. At the 17-month follow-up no evidence of primary or metastatic melanoma was present. This previously undescribed association of NCM, ECCL and placental nevomelanocytes provides strong support for the hypothesized causal role of anomalous neural crest morphogenesis and migration in the development of all three disorders. The genetic mechanism underlying these complex birth defects has been hypothesized to result from the action of lethal autosomal dominant genes surviving by mosaicism.

Focus on primary care: from nevus to neoplasm: myths of melanoma in pregnancy

Malignant melanoma is one of the few malignancies that regularly affect women during their childbearing years. Additionally, the incidence of melanoma has been increasing over the last several decades. Early diagnosis of stage I disease may lead to curative therapy; thus it is important for physicians and midwives to do a full examination of the skin. However, the myth that nevi may naturally grow or change during pregnancy has been shown not to be true and should not delay a diagnostic evaluation of a suspicious nevus. Older studies had theorized a worse outcome for pregnant women with melanoma. However, multiple controlled series and investigations have found that stage for stage this cancer is not affected adversely by pregnancy. Prognosis, recurrence, and incidence of melanoma seemed to be unaffected. Estrogen-containing oral contraceptives, as well as hormone replacement therapy, have no adverse affect on the disease.