Blue nevi, which are characterized by collections of pigment-producing melanocytes in the dermis, have a variety of clinicopathological characteristics. Plaque-type blue nevus (PTBN) is a variant of blue nevi. PTBN presents at birth or arises in early childhood, and it shows a combination of the features found in common blue nevus and cellular blue nevus. It is typically found on the dorsal surface of the hands and feet or on the head and neck, and it is usually benign and stable over time. However, reports have occasionally described malignant melanomas developing in or associated with a PTBN. Malignant blue nevi are most commonly found on the scalp. We report the case of an 88-year-old woman with a malignant melanoma associated with a PTBN of the cheek.
A blue nevus is a neoplasm composed of pigmented dendritic dermal melanocytic cells in the reticular dermis. There are three types of benign blue nevi (common blue nevus, cellular blue nevus, and combined blue nevus) in addition to malignant blue nevi [
An 88-year-old woman with no significant medical history presented with an enlarging plaque on her right cheek (
The lesion was removed by surgical excision. After surgical excision, the skin and soft tissue were covered by a split-thickness skin graft. After the operation, the patient healed well without any complications. However, a histopathological examination of the excised tissue showed atypical fusiform and epithelioid melanocytes containing granular or dense melanin pigment, which extended from the lower dermis to the subcutaneous layer. An immunohistochemical examination showed that the tumor cells and melanocytes were positive for HMB-45, MART-1, and S-100. The Ki-67 proliferation index was approximately 50% (
After the diagnosis of malignant melanoma associated with PTBN, enhanced computed tomography (CT) and magnetic resonance imaging (MRI) were performed. The mass showed high intensity on T1-weighted MRI and various intensities on T2-weighted imaging. Both CT and MRI showed a soft tissue tumor on the right cheek area without bone invasion. The possibility of metastasis was ruled out by a work-up that included chest CT, whole-body positron emission tomography-CT, a bone scan, and neck CT. We planned a second operation, which was performed under general anesthesia 22 days after the first surgery. Wide excision with supraomohyoid neck dissection and superficial parotidectomy were performed. The invasion depth was 11 mm and the safety margin was set to 2 cm [
There are three types of benign blue nevi (common blue nevus, cellular blue nevus, and combined blue nevus), in addition to malignant blue nevus [
PTBN is a rare variant of blue nevus, which was first described by Upshaw et al. in 1947 [
Rare cases with features similar to PTBN have been reported as “congenital segmental dermal melanocytosis,” characterized by a congenital onset and large bluish pigmentation of the chest or trunk; these lesions were common blue nevi, although one case was associated with cellular blue nevus [
However, Busam et al. [
These lesions commonly appear stable and frequently have benign histological reports. The potential of malignant melanoma associated with PTBN was first reported in 2012, and whether this lesion represents a lesion with similar biological behavior to malignant blue nevus or to a conventional malignant melanoma remains a matter of debate [
In conclusion, we report an unusual melanocytic tumor of the cheek, which was interpreted as a malignant melanoma arising in association with a PTBN. Our patient has had 1 year of being disease-free, but an uneventful postoperative course does not exclude the future potential for recurrence. The appropriate clinical management should involve frequent, long-term follow-ups.
computed tomography
magnetic resonance imaging
plaque-type blue nevus
No potential conflict of interest relevant to this article was reported.
The study was approved for exemption by the Institutional Review Board of Jeonbuk National University Hospital (IRB exemption No. CUH 2022-11-057).
The patient provided written informed consent for the publication and use of her images.
Conceptualization: Yoon Kyu Chung, Si-Gyun Roh. Data curation: Si-Gyun Roh, Min-Seok Kim, Jin Yong Shin, Nae-Ho Lee. Project administration: Yoon Kyu Chung, Si-Gyun Roh, Nae-Ho Lee. Visualization: Min-Seok Kim, Jin Yong Shin. Writing - original draft: Min-Seok Kim. Writing - review & editing: Si-Gyun Roh. Investigation: Yoon Kyu Chung, Min-Seok Kim, Jin Yong Shin, Ae Ri An, Nae-Ho Lee.
None.
A blue maculo-papular confluent plaque was seen on the right cheek area.
A histopathological examination showed atypical fusiform and epithelioid melanocytes containing granular or dense melanin pigment (hematoxylin and eosin stain, ×40).
In the second operation, the large skin and soft tissue defect were covered by a lateral arm free flap. (A) After wide excision, a skin and soft tissue defect occurred (B) Primary closure of the donor site was performed. (C) Result at postoperative 2 months.