Longitudinal black nail (nail nevus), the “mother” of the nail is sick!
Department of Plastic and Reconstructive Surgery, The First Affiliated Hospital of Zhengzhou University
Liu Lin, Li Guangshuai
Longitudinal black nail is a group of diseases that manifest clinically as brown or black bands from the root to the distal end of the nail on the bed of the finger (toe) nail. The most common of these is nail nevus, the “mother” of the nail. Liu Lin, Plastic Surgery Department, Zhengzhou University First Affiliated Hospital
I. General concept
Longitudinal black nail caused by melanocyte proliferation includes freckle-like nevus, nail mother nevus, nail mother melanoma, nail plate melanoma or sub nail melanoma.
1.Nail nevus
It is an epithelial pigmented nevus or a mass of active melanocytes in the nail matrix that causes the grown finger (toe) nail to contain a large amount of melanin. Typical nail mother nevus mostly occurs in adolescents, congenital or acquired; several millimeters to the whole nail, clear boundary, single or multiple, light brown or black; nail and toenail have no obvious specificity; nail mother nevus accounts for 48% of longitudinal black nail in children VS 12% in adults Pathological diagnosis most children are junctional nevus; the possibility of nail mother nevus progressing to melanoma cannot be excluded.
2.Melanoma of nail unit
It includes nail unit melanoma and subunit nail (bed) melanoma. The proportion of nail unit melanoma in all melanomas is 0.7%-3.5%; typical cases are advanced once detected; literature reports 5-year survival rate 16%-87%; poor prognosis is directly related to insufficient recognition and delayed diagnosis; occurs at any age; nail unit melanoma is not significantly related to ultraviolet light; racial aggregation The clinical presentation is mainly related to the primary site (nail matrix OR nail bed). The first symptom of nail matrix melanoma is longitudinal black stripes of varying widths on the nail plate in 70% of cases, which may be caused by melanoma destruction and compression of nail matrix epithelial cells; electron dermatoscopy shows uneven color, irregular spacing, varying thickness, and longitudinal fracture of the nail plate. The nail bed ulcers and bleeding suggest tumor progression; nail bed ulcers need to be differentiated from nail bed septic granuloma.
Early diagnosis of nail melanoma
1.ABCDEF principle
A Age= age (pearly in 5th-7th decades), Asian, African-Americans, Native Americans.
B Color mottling= brown to black band width breadth of 3 mm or more with variegated borders width >3 mm.
C inappropriate treatment= change in nail band despite treatment.
D number of nails involved = digit.
E staining involving the perinail= extension of pigment onto the proximal and/or lateral nailfold (Hutchinson’s sign).
F family history of melanoma = family or personal history of dysplastic nevus or melanoma.
2. Hutchinson’s sign
Although it cannot be used as direct evidence for the early diagnosis of nail melanoma, it is one of the strong clues for early diagnosis, and its presence suggests the need for biopsy to clearly diagnose and exclude melanoma.
3.Dermatoscopy
Under dermatoscopy, the coloring strips of nail plate and sub nail melanoma are uniformly colored and regular thin lines; the strips of nail melanoma are irregular, with blurred edges, and are diffuse. This examination helps to make accurate diagnosis of nail unit melanoma, but pathological histological diagnosis is ultimately required.
4.Indication of biopsy-exclusion of melanoma
①Lack of homogeneity of the pigmentation, with bands or lines of different color Diverse color, or colorful.
②Presence of nail plate fissuring or splitting deck cracking or fissures.
③Proximal part of the band broader than the distal (triangular shape) proximal end stripes wider than the distal end (triangular)
④Blurred lateral borders of the band Stripes edge blurred
⑤Pigmentation of the periungual skin (Hutchinson’s sign) perineural staining.
Follow-up recommendations
Children can be followed up until adolescence: follow-up is recommended for children younger than 12 years of age, but is often rejected by parents, who are concerned about malignancy during the follow-up process and the possibility that the black nail strips may widen with age.
Adults: >40 years of age There is no unified consensus on the follow-up of adults, and there is a lack of large-scale prospective clinical studies; once the above-mentioned red flags appear, immediate surgical excision and pathological histological examination are recommended.
IV. Surgical treatment
Black nail width < 3 mm: complete excision of the nail plate, nail bed, nail fold and nail matrix infiltrated by the lesion to the depth of the finger (toe) periosteum, and direct surgical closure of the nail plate, nail bed and nail fold.
Black nail width > 3mm: remove the diseased finger (toe) nail first by nail extraction, then complete excision of the proximal nail fold, nail matrix and nail bed in the upper layer of the finger (toe) periosteum, drilling holes in the periosteum at 2-3mm intervals to the medullary cavity, strengthening surgical dressing to promote the growth of granulation tissue, and finally scar healing to replace the nail bed and finger (toe) nail or take full thickness skin to cover the trauma, repair the nail bed, nail matrix and nail fold, and the finger (toe) nail no longer grows. The nail will no longer grow.
The importance of rapid intraoperative pathological histological examination is emphasized.
After surgery, the nail plate, nail bed and nail matrix infiltrated by the lesion will be completely excised and sent for pathological histological examination; in case of nail nevus or benign melanocytic hyperplasia, holes will be drilled at 2-3 mm intervals in the periosteum of the nail bed defect to the medullary cavity, surgical dressing changes will be intensified to promote the growth of granulation tissue, and finally scar healing will replace the nail bed and finger (toe) nail . When the lesion invades the entire nail plate, full-thickness skin sheets can also be used to cover the wound. If melanoma is confirmed, toe (finger) amputation in the metatarsophalangeal and metacarpophalangeal planes is performed, and thumb reconstruction can be performed at the same time after thumb amputation.
Postoperative comprehensive anti-tumor therapy (immunotherapy, biological therapy, etc.) is performed.