Large plaque‐type blue naevus with subcutaneous cellular nodules

We report a new case of ‘large plaque‐type blue naevus (PTBN) with subcutaneous cellular nodules’ involving the breast. A 25‐year‐old‐woman presented with a large plaque, 140 × 100 mm in size, on the right chest wall involving the right breast, associated with recent subcutaneous nodules. Histopathological examination revealed features of cellular and common blue naevus. Dermatoscopy was performed, and the diagnosis of PTBN was made. PTBN is a rare condition with an imprecise prognosis. In cases of PBTN lesions on the head, clinicians must keep in mind the risk of malignant transformation of PTBN or an association with cutaneous neurocristic hamartoma. For this new variant of PTBN appearing on the trunk, we propose close monitoring of the patient if surgical excision is impossible.     

Melanoma ex blue nevus: two cases resembling large plaque‐type blue nevus with subcutaneous cellular nodules

Large plaque‐type blue nevi with subcutaneous cellular nodules are rare tumors occurring on the trunk with deep extension into underlying soft tissues. The histopathologic appearance consists of deep nodules resembling cellular blue nevi with interspersed foci of common blue nevus. Conservative management has been recommended, and metastases have not been observed. This report discusses two cases with microscopic features of large plaque‐type blue nevi with subcutaneous cellular nodules in which comparative genomic hybridization showed chromosomal aberrations typical of melanoma. In both cases, the nodules showed gains involving chromosome 6p and losses involving chromosome 6q, which are among the most commonly found aberrations in melanoma. These copy number changes were not present in the less cellular surrounding areas that appeared characteristic of blue nevus. These cases illustrate that large blue nevi with a deep, multi‐nodular configuration should be interpreted with caution, and that superficial biopsies of such lesions can be misleading. Molecular techniques can provide valuable insights in these types of difficult melanocytic neoplasms.     

Recurrent nodules in a periauricular plaque‐type blue nevus with fatal outcome

Plaque‐type blue nevus is a rare variant of blue nevus characterized by grouped nodules displaying histomorphological features of a cellular blue nevus. We report the clinical, histopathologic and immunohistologic features of a patient with recurrent nodules in a periauricular plaque‐type blue nevus with malignant transformation and fatal outcome. The nevus was characterized clinically by childhood onset, with slow enlargement during adolescence. At age 16, the patient presented with nodules located retroauricularly. Several surgical excisions with the intent of complete removal of the nodules and the nevus were performed. Histopathological, dermal and subcutaneous proliferations of pigmented melanocytes with melanophages were detected. The nodules showed some cellular atypia and few mitotic figures, (Ki67 estimated <1%). At age 20, the patient developed new nodules retroauricular, with histopathology similar to previous lesions; however, the proliferation rate was higher. A comparative genomic hybridization (CGH) showed chromosomal changes indicative of melanoma. At age 25, the patient developed multiple liver metastases and died after 4 weeks. A sequencing of the tumor DNA revealed a GNAQ Q209P mutation, whereas mutations of GNA11, BRAF, NRAS and cKIT were not detected. This case shows that nodules in plaque‐type blue nevus may have malignant potential which may be uncovered by CGH.     

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.     

Giant alopecic nodule of the scalp: unusual presentation of a cellular blue naevus in an adult

A giant cellular blue naevus of the scalp is described in a man with presentation in the third decade of life. In contrast with previous reports of children with this condition, there was no abnormality of the underlying skull bones and no evidence of malignancy.     

Proliferative nodules of undifferentiated spindle cells arising in a large congenital melanocytic naevus

Proliferative nodules (PN) are benign lesions that arise in large congenital melanocytic naevi (LCMN). Clinically and histologically they can be difficult to differentiate from malignancies, which are also associated with LCMN. The PN in this case consisted of undifferentiated spindle cells and exhibited unusual histological features including negative stains for melanocytic markers (S100, HMB45 and MelA), negative stain for c‐Kit, high mitotic index and unusual morphology of the lesional cells. As a result, a firm histological classification could not be made, which posed a challenge for the clinical management.     

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.