Large plaque-type blue naevus with subcutaneous cellular nodules

The clinico-pathological spectrum of plaque-type blue naevi and their potential for malignant transformation

AIMS

Plaque-type blue naevi are rare melanocytic tumours presenting as large, pigmented plaques at birth or during childhood. There is a risk for malignant transformation, but no larger comprehensive studies exist and the diagnosis is challenging, especially on limited biopsy material. The aim is to describe the clinicopathological features and behaviour of the disease more comprehensively.

METHODS AND RESULTS

We retrieved eight plaque-type blue naevi, presenting as large, pigmented plaques (median = 7 cm; range = 3-26) most frequently affecting the scalp (four) followed by the cheek, arm, abdominal wall and gluteal cleft (one each), with a slight female predilection. Median age at time of biopsy was 39.5 years (range = 15-90), but three tumours had been present at birth and one since childhood. Histopathologically, the tumours were poorly circumscribed and composed of cellular fascicles of uniform spindle cells in a background of variably prominent pigmented dendritic cells affecting dermis and subcutaneous tissues. The majority had mutations in GNAQ. One tumour showed malignant transformation, characterised by an expansile nodule of pleomorphic epithelioid melanocytes with rhabdoid morphology, high mitotic activity and areas of necrosis. This patient developed metastatic melanoma to lymph nodes. All patients are alive with a median follow-up of 60 months.

CONCLUSION

Plaque-type blue naevi are diagnostically challenging tumours with risk for malignant transformation. Awareness and familiarity with the salient clinicopathological features are necessary for reliable diagnosis, and long-term clinical follow-up is required to monitor for malignant transformation.

GRM1 Gene Fusions as an Alternative Molecular Driver in Blue Nevi and Related Melanomas

Activating mutations in GNAQ, GNA11, CYSLTR2, and PLCB4 genes are regarded as the main oncogenic drivers of blue nevi (BN) and blue malignant melanocytic tumors. Here we report 4 cases of blue melanocytic neoplasms devoid of these mutations but harboring GRM1 gene fusions. In this short series, there was no gender predominance (sex ratio, 1). The mean age at diagnosis was 40 years (range, 12-72). Tumors were located on the face (n = 2), forearm (n = 1), and dorsum of the foot (n = 1). Clinically, a plaque-like pre-existing BN was found in 2 cases, including a deep location; another case presented as an Ota nevus. Two cases were diagnosed as melanoma ex-BN, one as an atypical BN, and one as a plaque-like BN. Microscopic examination revealed a dermal proliferation of dendritic melanocytes in a sclerotic stroma. A dermal cellular nodule with atypia and mitotic activity was observed in 3 cases. Genetic investigation by whole exome RNA sequencing revealed MYO10::GRM1 (n = 2) and ZEB2::GRM1 (n = 1) fusions. A GRM1 rearrangement was identified by fluorescence in situ hybridization in the remaining case. SF3B1 comutations were present in the 2 melanomas, and both had a MYO10::GRM1 fusion. Array comparative genomic hybridization was feasible for 3 cases and displayed multiple copy number alterations in the 2 melanomas and limited copy number alterations in the atypical BN, all genomic profiles compatible with those of classical blue lesions. GRM1 was overexpressed in all cases compared with a control group of blue lesions with other typical mutations. Both melanomas rapidly developed visceral metastases following diagnosis, with a fatal outcome in one case and tumor progression under palliative care in the other. These data suggest that GRM1 gene fusions could represent an additional rare oncogenic driver in the setting of BN, mutually exclusive of classical canonical mutations, especially in plaque-type or Ota subtypes.

Large Plaque-type Blue Nevus with GNAQ Q209P Mutation, Involving Mammary Gland Tissue: Under-Recognized Mammary Condition as an Origin of Primary Mammary Melanocytic Tumors

ABSTRACT

Plaque-type blue nevus is a rare variant of blue nevi that was first described in 1954. This article presents clinical, macroscopic, histopathological, and genetic findings for a case of large plaque-type blue nevus expanding into the mammary gland tissue as well as the skin of the right breast. A 63-year-old woman presented with a congenital, large, blue-colored macule limited to the hypochondriac area of the right breast. A nodule 8 mm in diameter was also present in the mammary gland tissue. Magnetic resonance imaging was unable to detect diffuse melanin deposition in the mammary gland tissue, but pigmentation in the whole mammary parenchyma was observed in the cut surfaces of the mastectomy specimen. Histopathology revealed a sparse distribution of dendritic melanocytes in whole sections of the mammary fibrous tissue and partial sections of the dermis. The histopathological criteria for atypical cellular blue nevus were fulfilled for the mammary tumor. Nodal blue nevus was diagnosed in the sentinel lymph node. Sanger sequencing confirmed the GNAQ Q209P mutation, which was also identified in all 4 literature cases of plaque-type blue nevus, but rarely in conventional blue nevi and uveal melanoma. It should be noted that plaque-type blue nevus can expand into the mammary gland tissue, even if the pigmented lesion does not exist on the overlying breast skin. The mammary condition can be the origin of primary mammary melanocytic tumors. Mosaicism of the GNAQ Q209P mutation can be a characteristic genetic alteration to extensive blue nevi, including plaque-type blue nevus.

Agminated blue nevus with a GNAQ mutation: A case report and review of the literature

Agminated blue nevi are dermal melanocytic proliferations that classically present as dark blue macules or papules in a grouped, linear, or blaschkoid distribution. In their more common sporadic form, blue nevi manifest in young adulthood as solitary blue papules or macules on the scalp, face, hands, or feet. By contrast, agminated blue nevi tend to manifest earlier in life, and are distributed more evenly across anatomic sites. Recent studies have identified mutations in sporadic blue nevi in the genes encoding G Protein subunit alpha Q and G protein subunit alpha 11 (GNAQ and GNA11). It is unknown whether agminated blue nevi share the same genetic changes. In the present paper, we present a case of agminated blue nevus on the wrist, and identify an activating mutation (c.626A > T, p.Glu209Leu) in GNAQ. We hypothesize that GNAQ/GNA11 activating mutations arising earlier during development may trigger agminated blue nevi, explaining the broader field of involvement in these cutaneous lesions.

Agminated segmental plaque-type blue nevus associated with hypertrichosis and soft tissue hypertrophy: Report of a case and review of the literature

Blue nevi are common skin neoplasms that typically present as asymptomatic solitary papules, although they may rarely occur in an agminated configuration. We describe a case of agminated blue nevus in a segmental facial distribution associated with soft tissue hypertrophy and hypertrichosis in a 16-year-old boy and present a review of the literature. Although they are generally considered to be benign, concurrent soft tissue changes occurring within an agminated blue nevus should be investigated thoroughly to exclude alternate diagnoses.

Melanoma arising from a plaque-type blue naevus with subcutaneous cellular nodules of the scalp

Plaque-type blue naevus (PTBN) is a very rare variant of blue naevus (BN). The potential malignancy of subcutaneous cellular nodules (SCN) in PTBN was discovered in 2012, and there is currently no clear consensus on prognostic factors or management guidelines of such lesions. PTBN on the scalp have not been described in the literature. We report the clinical, histopathological and immunohistological features of a 50-year-old man who presented with a 30-year history of scalp PTBN, with malignant proliferation of nodular elements and fatal outcome 8 years later. This case suggests that long-term monitoring of patients with PTBN is required. Early surgical removal of such lesions should be considered, especially in the presence of any case of enlargement or change.

The long history of a melanoma associated with a congenital large plaque type blue nevus with subcutaneous cellular nodules

The term large plaque type blue nevus with subcutaneous cellular nodules (LPTBN-SN) refers to a huge blue nevus, usually located on the trunk, that develops subcutaneous nodules many years after the lesion has appeared. The potential malignancy of an LPTBN-SN was only discovered in 2012.

We report the case of a 56-year-old Caucasian man that developed a cutaneous melanoma on an LPTBN-SN of the trunk. The first diagnosis was made more than 10 years before his death due to melanoma metastasis.

The case reported here highlights the malignant potential of an LPTBN-SN, the very long course even without treatment and the possible coexistence of benign, borderline or malignant subcutaneous nodules in the same LPTBN-SN.

Patients with large congenital blue nevi should be advised on the potential oncologic transformation of these lesions, the importance of follow-ups should be emphasized and, whenever possible, a preventive complete surgical removal should be evaluated before subcutaneous nodules develop.

Atypical Spitz Tumor Arising on a Congenital Linear Plaque-Type Blue Nevus: A Case Report With a Review of the Literature on Plaque-Type Blue Nevus

The plaque-type blue nevus (PTBN) is a rare variant of blue nevus, of which only a few reports are described. A nodular growth within a preexistent PTBN should always alert to the possibility of malignant transformation. The authors report the first case of an atypical Spitz tumor arising on a congenital linear PTBN in a 60-year-old woman. The diagnosis of “atypical Spitz tumor” is here used to describe a microscopic “gray zone” in which it is not possible to differentiate with adequate certainty between a Spitz nevus and a spitzoid melanoma. This report adds to and summarizes the small body of literature describing PTBN and discusses diagnostic and clinical implications.

Large agminated cellular 'plaque-type' blue nevus surrounding the ear: a case and review

Large or giant cellular blue nevi are usually congenital and represent a challenge for the physician. Close anatomic structures may be altered by the size of the moles. In this article, we report the case of an uncommon large, agminated, cellular blue nevus of the 'plaque type' in a 42-year-old female. Due to the risks of malignant melanoma development on a large or giant blue nevus, we highlight the importance of proper histopathological diagnosis. Furthermore, because of the possibility that the nevus may invade the bone and cerebral tissues, we discuss the indication of a radiological diagnosis. The accurate correlation to clinical and histopathological findings and appropriate multidisciplinary management can save the lives of patients.

Melanoma arising in a large plaque-type blue nevus with subcutaneous cellular nodules

Melanoma may arise in association with and/or simulate the appearance of a cellular blue nevus. The distinction of a cellular blue nevus with atypical features from blue nevus-like melanoma can be difficult. One rare setting, in which one may face this diagnostic challenge, is nodule formation in a large plaque-type blue nevus. We have previously reported 2 patients with cellular blue nevus-like subcutaneous nodules without overt malignant features and indolent clinical behavior. Herein we report a patient who developed malignant melanoma in association with a large plaque-type blue nevus. A 46-year-old woman with a history of "cellular blue nevus" of the breast that developed 7 years earlier during pregnancy had soft tissue nodules at the prior surgical site. She was found to have melanoma associated with a large plaque-type blue nevus, which involved the skin and subcutis of the chest wall and extended into breast parenchyma. Ten years after mastectomy and axillary node dissection with negative lymph nodes, the melanoma recurred as a subcutaneous chest wall nodule. Cytogenetic analysis revealed a number of aberrations, including deletion of 6q and gains of 6p and 8q. The patient then developed visceral metastases, first to the liver, and died of widely metastatic melanoma. In contrast, the cytogenetic findings of a previously reported cellular blue nevus-like nodule in a patient with a large plaque-type blue nevus were normal. That patient is still alive with no evidence of melanoma 16 years after the surgical excision of the subcutaneous cellular blue nevus-like nodule.

Spindle cell melanocytic lesions: part II—an approach to intradermal proliferations and horizontally oriented lesions

Melanocytic lesions show great morphological diversity in their architecture and the cytomorphological appearance of their composite cells. Whereas functional melanocytes show a dendritic cytomorphology and territorial isolation, lesional nevomelanocytes and melanoma cells typically show epithelioid, spindled or mixed cytomorphologies, and a range of architectural arrangements. Spindling is common to melanocytic lesions, and may either be a characteristic feature or a divergent appearance. The presence of spindle cells may mask the melanocytic nature of a lesion, and is often disconcerting, either due to its infrequent appearance in a particular lesion or its interpretation as a dedifferentiated phenotype. Spindle cell melanocytic lesions follow the full spectrum of potential biological outcomes, and difficulty may be experienced judging the nature of a lesion due to a lack of consistently reliable features to predict biological behaviour. Over time, recognition of numerous histomorphological features that may portend a more aggressive lesion have been identified; however, the translation of these features into a diagnostic entity requires a gestalt approach. Although most spindle cell melanocytic lesions may reliably be resolved through this standard approach, problem areas do exist for the surgical pathologist or dermatopathologist. With this review (part II of II), we complete our discussion of spindle cell melanocytic lesions, in order to: (1) model a systematic approach to such lesions; and (2) provide familiarity with those melanocytic lesions which either typically or occasionally display a spindled cytomorphology.