Blue Nevi and Related Tumors

BRAF Mutated and Morphologically Spitzoid Tumors, a Subgroup of Melanocytic Neoplasms Difficult to Distinguish From True Spitz Neoplasms

Drivers of Spitz neoplasms include activating point mutations in HRAS and Spitz-associated genomic fusions. It has become evident that some BRAF -mutated melanocytic neoplasms can morphologically mimic Spitz tumors (STs). These have been termed BRAF mutated and morphologically spitzoid (BAMS). In this study, 17 experts from the International Melanoma Pathology Study Group assessed 54 cases which included 40 BAMS and 14 true STs. The participants reviewed the cases blinded to the genomic data and selected among several diagnostic options, including BAMS, ST, melanoma, and other. A total of 38% of all diagnostic selections in the BAMS cases were for BAMS, whereas 32% were for ST. In 22 of the BAMS cases, the favored diagnosis was BAMS, whereas in 17 of the BAMS cases, the favored diagnosis was ST. Among the 20 cases in the total group of 54 with the highest number of votes for ST, half were BAMS. Of BAMS, 75% had a number of votes for ST that was within the SD of votes for ST seen among true ST cases. There was poor interobserver agreement for the precise diagnosis of the BAMS (kappa = 0.16) but good agreement that these cases were not melanoma (kappa = 0.7). BAMS nevi/tumors can closely mimic Spitz neoplasms. Expert melanoma pathologists in this study favored a diagnosis of ST in nearly half of the BAMS cases. There are BAMS cases that even experts cannot morphologically distinguish from true Spitz neoplasms.

Histologic and Genetic Features of 51 Melanocytic Neoplasms With Protein Kinase C Fusion Genes

Fusion genes involving homologs of protein kinase C (PKC) have been identified in a variety of tumors. We report the clinical and histologic presentation of 51 cutaneous melanocytic neoplasms with a PKC fusion gene (involving PRKCA in 35 cases, PRKCB in 15 cases, and PRKCG in a single case). Most tumors were in young adults (median age, 29.5 years; range, 1-73 years) but some presented in newborns. Histologically, 42 tumors were classified as benign, presenting predominantly as biphasic dermal proliferation (88%) with nests of small melanocytes surrounded by fibrosis with haphazardly arranged spindled and dendritic melanocytes, resembling those reported as "combined blue nevi." Most tumors (60%) were heavily pigmented and in 15%, hyperpigmented epithelioid melanocytes were present at the dermoepidermal junction. Two lesions were paucicellular and showed marked sclerosis. Three tumors, including 2 proliferating nodules, were considered intermediate grade. Six tumors had sheets of atypical melanocytes infiltrating the dermis and were classified as melanomas. Two of the melanomas displayed loss of BAP1 nuclear expression. The median follow-up time was 12 months, with 1 patient alive with metastatic disease and 1 dying of their melanoma. These results suggest that melanocytic tumors with PKC fusion genes have characteristic histopathologic features, which are more similar to blue nevi than to pigmented epithelioid melanocytomas. As is the case with GNA-mutated blue nevi, they can progress to melanomas via BAP1 inactivation and metastasize.

Agminated presentation of fusion-driven melanocytic neoplasms

BACKGROUND

The conventionally understood pathogenesis of agminated Spitz nevi includes a mosaic HRAS mutation followed by copy number gains in 11p. However, we have recently observed agminated presentations of fusion-driven melanocytic neoplasms.

METHODS

We retrieved cases from our database of benign fusion-induced melanocytic neoplasms with an agminated presentation. Both the primary lesion and the secondary lesion were sequenced. TERT-promoter mutational testing and the melanoma fluorescence in situ hybridization assay were also performed.

RESULTS

Three cases were included. Two had a PRKCA fusion (partners ATP2B4 and MPZL1) and one had a ZCCHC8::ROS1 fusion. None of the cases met morphologic or molecular criteria for malignancy. There was no evidence of tumor progression in secondary lesions. The same fusion was identified in the primary and secondary lesions. None of the patients developed evidence of nodal or systemic metastasis.

CONCLUSIONS

We present accumulating evidence that fusion-driven melanocytic neoplasms can present with an agminated presentation. The differential diagnosis of an agminated presentation versus a locally recurrent or potentially locally metastatic tumor is critical, and accurate diagnosis has significant prognostic and therapeutic consequences for the patient. As with HRAS mutations, fusion-driven melanocytic tumors may have an agminated presentation.

Next-generation Sequencing as a Potential Diagnostic Adjunct in Distinguishing Between Desmoplastic Melanocytic Neoplasms

Desmoplastic melanomas (DMs) are often challenging to diagnose and ancillary tests, such as immunohistochemistry, have limitations. One challenge is distinguishing DM from benign desmoplastic melanocytic neoplasms. In this study, we explored the utility of next-generation sequencing data in the diagnosis of DMs versus desmoplastic Spitz nevi (DSN) and desmoplastic nevi (DN). We sequenced 47 cases and retrieved 12 additional previously sequenced clinical cases from our dermatopathology database. The 59 total cases were comprised of 21 DMs, 25 DSN, and 13 DN. The DMs had the highest tumor mutation burden at 22 mutations/megabase (m/Mb) versus the DSN (6 m/Mb) and DN (8 m/Mb). Truncating mutations in NF1 resulting in a loss-of-function were exclusive to the DM cohort, identified in 8/21 (38%) cases. Importantly, missense mutations in NF1 were nonspecific and seen with similar frequency in the different cohorts. Other mutations exclusive to the DMs included truncating mutations in TP53 , CDKN2A , and ARID2 . Among the DSN, 17/25 (68%) had an HRAS mutation or receptor tyrosine kinase fusion consistent with other Spitz tumors. Two cases in the DN cohort had missense mutations in BRAF without additional progression mutations and 2 other cases had mutations in GNAQ , supporting a diagnosis of a sclerosing blue nevus. The remainder of the DN had nonspecific mutations in various signaling pathways with few progression mutations. Overall, our study provides preliminary data that next-generation sequencing data may have the potential to serve as an ancillary diagnostic tool to help differentiate malignant and benign desmoplastic melanocytic neoplasms.

Modern Concepts in Melanocytic Tumors

The advent of molecular pathology has fueled unprecedented advances in the diagnosis and understanding of melanocytic tumors. These advances, however, have also generated concepts that may be difficult to grasp for clinical practitioners, who are not always conversant with the array of genetic techniques employed in the laboratory. These same practitioners, however, are being increasingly called on to provide treatments that are often based on the latest molecular findings for melanocytic tumors. We review the most recent concepts in the pathway classification of melanocytic tumors, including intermediate lesions known as melanocytomas. We examine the genetic and molecular techniques used to study these tumors, look at where they overlap, and discuss their limitations and some of the most difficult-to-interpret results.

Melanoma arising in extracutaneous cellular blue nevus: report of two cases with comparison to cutaneous counterparts and uveal melanoma

AIMS

Blue nevi are benign melanocytic lesions that typically occur in the dermis. Melanoma arising in blue nevus is rare and shows a molecular profile distinct from conventional forms of cutaneous melanoma and more similar to uveal melanoma and central nervous system (CNS) melanocytomas. In contrast to conventional cutaneous melanoma, these tumor types typically show activating driver mutations in GNAQ or GNA11, a low mutational burden without evidence of a UV signature, and a reproducible pattern of chromosomal copy number changes. Blue nevi can also occur at extracutaneous sites. Here we report two cases of melanoma arising in extracutaneous blue nevus and compare their molecular features to cohorts of melanoma arising in cutaneous blue nevus (5 patients) and uveal melanoma (6 patients).

METHODS AND RESULTS

We describe the clinical, histomorphologic, immunohistochemical, and molecular findings in these two cases of melanoma arising in extracutaneous blue nevus. We compare their molecular profiles to melanomas arising in cutaneous blue nevus and uveal melanoma using a targeted next-generation DNA sequencing platform and find striking similarities between all three groups.

CONCLUSIONS

The close relationship between blue nevus-associated melanomas, regardless of their anatomic site, supports and validates the concept of melanoma arising in extracutaneous blue nevus and suggests that the two groups share common pathogenic mechanisms. The similarity of both groups to uveal melanoma in turn supports the close relationship between blue nevus-associated melanoma, uveal melanoma, and CNS melanocytoma, and their distinction from conventional UV-associated melanoma. These findings have important implications for prognosis and therapy.

Blue nevi of the palpebral conjunctiva: report of 2 cases and review of literature

PURPOSE

To describe two patients with blue nevi of the palpebral conjunctiva and to review the existing literature on common and cellular blue nevi of the conjunctiva.

METHODS

Report of two cases and literature review.

RESULTS

We present two cases of blue nevi in the palpebral conjunctiva: an atypical cellular blue nevus of the left upper eyelid and a common blue nevus around the lacrimal punctum of the left lower eyelid. Both patients underwent full thickness eyelid excision with wide margins. There was no tumor recurrence at 11 and 4 months postoperatively.

CONCLUSIONS

Blue nevi are a group of melanocytic tumors that rarely involve the ocular adnexa. They may arise in the palpebral conjunctiva and should be considered in the differential diagnosis of pigmented lesions in this location as they can mimic melanoma.

Compound blue nevus: A misleading pigmented melanocytic tumor

Compound blue nevus had clinical and histological similarities with other heavily pigmented melanocytic tumor, like the pigmented epithelioid melanocytoma. Distinctive genomic aberrations have allowed differentiating it. The defining characteristic of blue nevi family is the presence of activating mutations in the G protein α-subunits, GNAQ and GNA11.

Primary Cilia Are Preserved in Cellular Blue and Atypical Blue Nevi and Lost in Blue Nevus-like Melanoma

Distinguishing cellular blue nevi (CBNs) and atypical CBNs from blue nevus-like melanoma (BNLM) can be diagnostically challenging. Immunohistochemistry may inform the diagnosis in a subset of cases but is not always diagnostic. Further, ancillary molecular testing is expensive and often requires significant tissue to complete. Primary cilia are cell-surface organelles with roles in signal transduction pathways and have been shown to be preserved in conventional melanocytic nevi but lost in melanoma. Immunofluorescence staining of primary cilia can be performed using a single standard-thickness formalin-fixed paraffin-embedded tissue section and has a turnaround time similar to immunohistochemistry. The percentage of tumoral melanocytes retaining a primary cilium is quantified and reported as the ciliation index. In the current study, we explored the utility of the ciliation index in a series of 31 blue nevus-like lesions, including CBNs (12), atypical CBNs (15), and BNLM (4). The average ciliation index for the CBNs was 59±18%, with a median of 60 (range: 28 to 87). The average ciliation index for atypical CBNs was 59±23, with a median of 59 (range: 20 to 93). The average ciliation index for BNLM was 4±3, with a median of 3 (range: 1 to 8). There was no significant difference in ciliation index between the CBN and atypical CBN categories. There was a significant difference between CBN and BNLM and between atypical CBNs and BNLM (P<0.001 for each). Here, we show that ciliation index is a quantitative diagnostic tool useful in the setting of blue nevus-like neoplasms, with benefits including cost and time efficiency.

Giant Congenital Blue Nevus Presenting as Cutis Verticis Gyrata: A Case Report and Review of the Literature

OBJECTIVES

Cerebriform intradermal nevus and giant congenital blue nevi are rarely reported melanocytic nevi with clinical and histopathologic similarities. Both are known to produce cutis verticis gyrata. We report a significantly large occipital scalp congenital blue nevus with secondary cutis verticis gyrata. The aim of this report is to increase clinical awareness of this entity, highlight histopathologic and mutational features of cerebriform intradermal nevi and giant congenital blue nevi, and stress the importance of clinicopathologic correlation for diagnosis.

METHODS

Case report and review of the literature.

RESULTS

A 20-year-old Asian male presented with a long-standing, large (20 cm × 30 cm), exophytic tumor at the occipital scalp and posterior neck. The skin overlying the lesion was arranged in thick folds resembling the surface of the brain, devoid of hair follicles, and discolored by salt-and-pepper pattern hyperpigmentation. After correlating the clinical and histopathologic findings, we diagnosed giant congenital blue nevus with secondary cutis verticis gyrata. Staged surgical excision was performed with subsequent treatment for hypertrophic scarring and occipital alopecia.

CONCLUSIONS

Cerebriform intradermal nevus and giant congenital blue nevus have overlapping histologic and clinical features. Head and neck surgeons should be aware that nomenclature of these tumors is subjective and often imprecise. Diagnosis requires correlation of clinical findings, patient history, and histopathology. Surgical excision is advised due to rare malignant transformation potential.

Atypical Cellular Blue Nevus With Necrosis Mimicking Melanoma Ex-Blue Nevus

ABSTRACT

Histologic distinction between melanoma ex-blue nevus and cellular blue nevus (CBN) can often be difficult, but features supporting melanoma include infiltrative growth pattern, frequent mitoses, cytologic atypia and pleomorphism, cell crowding, and tumor necrosis. Unfortunately, these features are not constantly dependable and frequently borderline lesions exist, so-called atypical CBN, which lack explicit malignant features. Furthermore, some CBN and atypical CBN show an assortment of features, which may lead to their misdiagnosis as melanoma, but to date necrosis is generally absent. We present an unusual case of an atypical cellular blue nevus with extensive necrosis mimicking melanoma ex-blue nevus.

Disseminated Eruptive Blue Nevi in a Young Adult Patient

Common blue nevi tend to be singular or localized, with multiple eruptive blue nevi being a rare occurrence. We report the case of a young adult who presented with multiple asymptomatic lesions that had appeared gradually over a few years. Physical examination revealed 30 distinct, blue-gray macules diffusely over the medial buttocks, lower back, and dorsal arms. Histopathology showed pigmented dendritic melanocytes with associated melanophages, features characteristic of blue nevus. This case demonstrates that eruptive blue nevi can present as numerous, disseminated lesions over multiple anatomic sites. Recognition of the various patterns of eruptive blue nevi and their benign nature can reduce unnecessary biopsies and work-up.

Primary intra-abdominal melanoma arising in association with extracutaneous blue naevus: a report of two cases

AIMS

Blue naevi are uncommon dermal melanocytic neoplasms characterised by GNAQ/GNA11 mutations, which very rarely progress to melanoma. Such melanomas also often have BAP1 mutations, and lack genetic events associated with conventional melanoma. Exceptionally, blue naevi arise in extracutaneous locations; one melanoma arising in this setting has been reported. We report the clinicopathological, immunohistochemical and molecular genetic features of two cases of melanoma arising in extracutaneous blue naevus.

METHODS AND RESULTS

Both arose in males, aged 25 and 63 years, with no history of other melanocytic lesions, and presented as large, painful intra-abdominal masses. The tumours were dark-brown/black, multilobulated, involved small intestinal mesentery and consisted of a predominantly fascicular and spindled, but occasionally nested and epithelioid, proliferation of variably pigmented, relatively monotonous cells with pale cytoplasm and ovoid nuclei with mild to moderate atypia. Mitotic activity was variable but generally low. Both cases showed areas of conventional and cellular blue naevus. Recurrent tumour in one case showed predominantly epithelioid morphology and greater cytological atypia and mitotic activity. One case expressed Melan-A, SOX10 and CD117, with absent expression of S100 protein and DOG1; the other expressed Melan-A, HMB45 and S100 protein. Next-generation sequencing identified GNAQ and BAP1 mutations in one case and GNA11 mutation in the other. Both patients developed widespread metastatic disease.

CONCLUSION

Exceptionally rare, aggressive melanomas arising in extracutaneous blue naevi should be distinguished from metastatic melanoma, gastrointestinal stromal tumour and malignant melanotic nerve sheath tumour, especially given the significant therapeutic and prognostic differences between these different entities.

Clinicopathological study of blue nevi of the gastrointestinal (GI) tract: first case series

AIM

Blue nevus (BN) is a benign melanocytic proliferation that is typically cutaneous. Extracutaneous BN is infrequent and is reported in the mucosa of various organs. Gastrointestinal (GI) tract BN is rare. Here, we describe the clinicopathological findings of the largest series of GI tract BNs.

METHODS

A search of our Pathology Data System (1984-2019) identified six GI tract blue nevi. Clinical information, pathology reports and available H&E-stained section slides were reviewed.

RESULTS

Lesions predominated in the middle-aged adults (mean 54, range 27-80) with a slight female predominance (66%). Most cases arose in the rectum and colon (83%), with one gastric lesion (17%). Four cases were identified during endoscopic examination performed either for screening or for unrelated symptoms (66%). Two patients presented with rectal bleeding (33%) unassociated with the BN. Endoscopically, most lesions appeared as superficial hyperpigmented areas (83%). One case was described as abnormal mucosa (17%). Microscopically, the mucosa was involved in all of the cases (100%). One case showed submucosal extension in addition to the mucosal component (17%). Lesions showed a proliferation of bland spindle cells with abundant granular pigment. No nuclear atypia or mitoses were identified. Immunostains showed immunoreactivity for melanocytic markers. Follow-up information available for five patients showed no recurrences to date (mean follow-up 1 year).

CONCLUSIONS

BN is a benign melanocytic proliferation. It is important to be aware of the occurrence of such lesions outside of the skin and consider the possibility of BN when pigmented lesions are encountered in the GI tract.

The 2018 World Health Organization Classification of Cutaneous, Mucosal, and Uveal Melanoma: Detailed Analysis of 9 Distinct Subtypes Defined by Their Evolutionary Pathway

CONTEXT.—

There have been major advances in the understanding of melanoma since the last revision of the World Health Organization (WHO) classification in 2006.

OBJECTIVE.—

To discuss development of the 9 distinct types of melanoma and distinguishing them by their epidemiology, clinical and histologic morphology, and genomic characteristics. Each melanoma subtype is placed at the end of an evolutionary pathway that is rooted in its respective precursor, wherever appropriate and feasible, based on currently known data. Each precursor has a variable risk of progression culminating in its fully evolved, invasive melanoma.

DATA SOURCES.—

This review is based on the "Melanocytic Tumours" section of the 4th edition of the WHO Classification of Skin Tumours, published in 2018.

CONCLUSIONS.—

Melanomas were divided into those etiologically related to sun exposure and those that are not, as determined by their mutational signatures, anatomic site, and epidemiology. 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 basis of degree of associated solar elastosis. Low-CSD melanomas include superficial spreading melanomas and high-CSD melanomas incorporate lentigo maligna and desmoplastic melanomas. The "nonsolar" category includes acral melanomas, some melanomas in congenital nevi, melanomas in blue nevi, Spitz melanomas, mucosal melanomas, and uveal melanomas. The general term melanocytoma is proposed to encompass "intermediate" tumors that have an increased (though still low) probability of disease progression to melanoma.

Compound blue nevus: a reappraisal of the concept in the genomic era

We report a series of 21 compound blue nevi, a rare variant in the vast clinical and morphological spectrum of blue melanocytic proliferations. Clinically, they presented in young adults, with a slight female predominance. One-third were located on the dorsum of the foot. Morphologically, all cases displayed large dendritic melanocytes restricted to the deep layers of the epidermis. The compound component was central and evenly distributed. Melanocytic density ranged from scarce isolated cells to a confluent lentiginous architecture. In 12 of the 21 cases, junctional nests of small, bland, weakly pigmented melanocytes were associated. These nests became confluent in the most cellular cases. In all cases, a dermal component was immediately present underneath, mainly of cellular blue nevus-type. All cases were genetically confirmed to harbor either a GNAQ or GNA11 hotspot mutation. This study expands the morphological spectrum of blue nevi that should not be restricted to a strictly intradermal melanocytic proliferation.

A cellular blue nevus with pigmented epithelioid melanocytoma-like pattern on the ipsilateral upper arm associated with a congenital plaque-type blue nevus on the hand

A 36-year-old man presented with a subcutaneous nodule on the right upper arm. A small nodule had developed 8 years earlier, and grew in size, accompanied by a tingling sensation and numbness. In addition, he had a bluish irregular patch on the right hand since birth, which crossed from the palm to the dorsal hand. Skin biopsies from the hand showed a heavily pigmented melanocyte proliferation in the dermis with perieccrine, perivascular, and perineural involvement, and a diagnosis of congenital plaque-type blue nevus was made. The tumor on the arm was located closely along the median nerve, and was observed as a large black pedunculated round tumor. Histopathologically, the tumor on the arm consisted of densely packed tissue with nevoid cells without atypia in the larger nodular part, and heavily pigmented spindle and epithelioid melanocytes in the slender stalk area, which was diagnosed as cellular blue nevus with pigmented epithelioid melanocytoma-like pattern. Next-generation sequencing revealed GNAQ mutations in the hand lesion, and in the lesions on the arm. This case suggests that the areas of skin following the same neural distribution of a congenital plaque-type blue nevus on the extremities should be followed up for secondary changes.

Nevus Blue as a Sporadic Finding in a Patient with a Blue Toe?

BACKGROUND:

Blue nevus is an interesting finding, which aetiology and risk of locoregional and distant metastasis have not yet been fully clarified. It may be inherited or acquired, with sporadic cases usually presented as solitary lesions. It is often localised in the area of the head and less often on the arms, legs or trunk. Blue nevi are formations with relatively low but still possible potential for switching to melanoma.

CASE REPORT:

The patient we described was hospitalised for pronounced cyanosis of the small toe of the right foot, accompanied by painful symptoms at rest and pain symptoms for a few weeks. Using inpatient paraclinical and instrumental tests, the patient was diagnosed with cholesterol microembolism. During the dermatological examination, blue nevus on the contralaterally localised limb was also diagnosed as a sporadic finding. According to the patient’s medical history, the finding had existed for many years, but in the last few months, the patient has observed growth and progression in the peripheral zone of the nevus without any additional clinical symptoms.

CONCLUSION:

Due to the risk of progression to melanoma, the lesion was removed by radical excision, and the defect was closed by tissue advancement flap.

Spontaneous Venous Aneurysm: Report of a Non-traumatic Superficial Venous Aneurysm on the Distal Arm

Venous aneurysms are benign acquired vascular lesions. A 59-year-old man developed a lesion on his right wrist that would enlarge and flatten depending on whether his arm was dependent or elevated; he had no prior history of trauma to the site. Examination of his wrist revealed a soft, compressible nodule contiguous with venous structures in the area. The history and clinical appearance established the diagnosis of a superficial venous aneurysm. Venous aneurysms typically occur on extremities, either in the superficial or deep venous systems; a prior history of trauma is often elicited. Clinical observation may be appropriate for the management of venous aneurysms; however, symptomatic lesions often require excision. In conclusion, venous aneurysms often appear in adults; trauma may or may not precede their appearance. Asymptomatic lesions may be observed, whereas surgery may be necessary to resolve the condition if the aneurysm is symptomatic.