Longitudinal Melanonychia:

Role of tangential biopsy in the diagnosis of nail psoriasis

BACKGROUND

Histopathology can be crucial for diagnosis of inflammatory nail diseases. Longitudinal excision and punch biopsies are the most used techniques to obtain the tissue sample. However, there is a low clinical-histopathological correlation, besides the risk of nail dystrophy. Tangential excision biopsy (TB) is a well-established technique for the investigation of longitudinal melanonychia. TB could also be used to evaluate diseases in which histopathological changes are superficial, as in psoriasis.

OBJECTIVE

To study the value of TB in the histopathological diagnosis of nail psoriasis.

METHODS

This is a prospective and descriptive study of the clinical-histopathological findings of samples from the nail bed or matrix and nail plate of 13 patients with clinical suspicion of nail psoriasis. Biopsies were obtained through partial nail avulsion and TB.

RESULTS

In nine patients, the hypothesis of psoriasis was confirmed by histopathology; in one, the criteria for diagnosing nail lichen planus were fulfilled. The tissue sample of only one patient did not reach the dermal papillae, and, in four of 13 patients, the adventitial dermis was not sampled. No patient developed onychodystrophy after the procedure.

STUDY LIMITATIONS

In three patients, the clinical and, consequently, histopathological nail changes were subtle. Also, in one patient's TB didn't sample the dermal papillae.

CONCLUSIONS

TB is a good option to assist in the histopathological diagnosis of nail psoriasis, especially when appropriate clinical elements are combined. Using this technique, larger and thinner samples, short postoperative recovery time, and low risk of onychodystrophy are obtained.

Update on nail unit histopathology

Histopathologic evaluation of the nail unit is an essential component in the diagnosis of nail unit disorders. This review highlights recent updates in nail unit histopathology and discusses literature covering a wide range of nail disorders including melanoma/melanocytic lesions, squamous cell carcinoma, onychomatricoma, onychopapilloma, onychomycosis, lichen planus, and other inflammatory conditions. Herein we also discuss recent literature on nail clipping histopathology, a useful and noninvasive diagnostic tool that continues to grow in popularity and importance to both dermatologists and dermatopathologists.

Clinical and dermoscopic features of nail unit melanoma in an Australian nail clinic cohort

Nail unit melanoma carries diagnostic challenges conferring with its poor prognosis. This audit aims to characterise both clinical and dermoscopic features of nail unit malignant lesions and compare them with biopsied benign lesions. It focuses on informing future practice by aiding in the stratification and recognition of malignant diagnostic patterns in the Australian context.

Disorders of hyperpigmentation. Part I. Pathogenesis and clinical features of common pigmentary disorders

Disorders of hyperpigmentation are common and, depending on the extent and location of involvement, can affect the quality of life and pose a significant psychologic burden for patients. Given the similarities in presentation of the various causes of hyperpigmentation, it is often difficult to elucidate the etiology of these conditions, which is important to guide management. Furthermore, certain disorders, such as lichen planus pigmentosus and ashy dermatosis, have similar clinical and/or histologic presentations, and their classification as distinct entities has been debated upon, leading to additional confusion. In this review, the authors selected commonly encountered disorders of hyperpigmentation of the skin, subdivided into epidermal, dermal, or mixed epidermal-dermal disorders based on the location of pigment deposition, along with disorders of hyperpigmentation of the mucosa and nails. Melanocytic nevi, genetic disorders, and systemic causes of hyperpigmentation were largely excluded and considered to be outside the scope of this review. We discussed the pathogenesis of hyperpigmentation as well as the clinical and histologic features of these conditions, along with challenges encountered in their diagnosis and classification. The second article in this 2-part continuing medical education series focuses on the medical and procedural treatments of hyperpigmentation.

[Physiologic hyperpigmentation on darker skin]

Many, even common, normal variations and nuances of skin of color are less frequently described or often misinterpreted as pathological. Recognizing these physiologic changes is gaining relevance in our increasingly diverse patient population and enables the physician to encourage the acceptance by the patients as well as to manage our resources wisely. Therefore, we explain common hyperpigmentation on dark skin such as demarcation lines, mucosal hyperpigmentation, melanonychia striata, and circumscribed dermal melanocytosis. The aim of this article is to facilitate the classification of these phenomena in clinical practice.

Retrospective analysis of longitudinal melanonychia: A Chinese experience

OBJECTIVE

We aimed to analyze the clinical and histopathologic characteristics of longitudinal melanonychia (LM), explore the differences between adults and children, and propose some recommendations.

METHODS

Data on pigmentation, lentigo, subungual melanoma (SUM), and nail matrix nevus (NMN) were acquired for comparison.

RESULTS

Lesions on thumbs in the children's group were significantly fewer (p = 0.006) than in adults. Lesions on little fingers in children were more than in adults; the difference was statistically significant (p = 0.025). The widths of bands in adults were wider than in children (p < 0.001), and the duration and width were positively correlated (r = 0.474). There was more pigmentation in adults than in children; the difference was statistically significant (p = 0.005). NMN was reported in 56.1% children and 34.3% adults; the difference was statistically significant (p = 0.005). Adults had six SUM cases, whereas none in children; the difference was statistically significant (p = 0.006). The recurrence rate in adults was significantly higher than in children (p = 0.019).

CONCLUSION

The widths of bands increase with the course, indicating that LM may be progressive. The four pathological types have different distributions with age, and each type requires different treatment. The lower recurrence rate in children suggests that LM needs diagnosis and appropriate treatment as soon as possible.

Distribution of cellular remnants of melanocytes in the nail plate: Clue to the diagnosis of subungual melanoma

BACKGROUND

Previous studies reported that cellular remnants in the nail plate could be a diagnostic clue for subungual melanoma (SUM). We sought to characterize the histopathologic features of cellular remnants in the nail plates of SUM patients.

METHODS

A retrospective case-control study was conducted in a single tertiary center from 2012 to 2019. Twenty-three patients with pathologically diagnosed SUM and eight nail matrix nevi (NMN) patients were recruited. The analysis of the nail plate specimens focused on large cellular remnants of melanocytes (LCRMs). Longitudinal linear density and vertical distribution pattern of the LCRMs were scrutinized for possible features distinguishing SUM from NMN.

RESULTS

The median linear density of the LCRMs was significantly higher in the SUM samples than in the NMN samples. LCRMs in the SUM samples were more dorsally distributed than those in the NMN samples. In invasive SUM, LCRMs were more likely to be found in the dorsal part of the nail plate compared to SUM in situ.

CONCLUSION

Nail plate specimens should not be overlooked in the histopathological examination of melanonychia. High-density LCRMs with more dispersion to the dorsal side might be suggestive of SUM.

Management of Nail Unit Melanoma

Nail unit melanoma is an uncommon form of melanoma with worse prognosis compared with nonacral cutaneous melanoma. Nail unit melanoma is often diagnosed at a late stage. Clinical and dermoscopic features may suggest a diagnosis of nail unit melanoma, but confirmation requires histologic analysis. Like the clinical diagnosis, histopathologic diagnosis of nail unit melanoma is also difficult. The surgical management of nail unit melanoma has evolved from aggressive amputations to digit-sparing approaches. This article reviews the clinical presentation, diagnosis, and surgical treatment of nail unit melanoma to promote early diagnosis and rational surgery.

Subungual Nail Erythrasma Presenting as Melanonychia: A Rare Finding

Nail pathology may reflect a wide array of localized and systemic dermatological conditions. Certain nail findings such as melanonychia can create diagnostic challenges even to nail experts. We report a case of a 78-year-old man who presented with melanonychia of the great toe. Nail clipping showed focal melanin deposition, and dermoscopy demonstrated a region of localized erythema in the lunula concerning for possible melanocytic neoplasm. Subsequent nail biopsy showed numerous vertically oriented filamentous bacteria and coccobacilli within the nail plate consistent with a diagnosis of subungual nail erythrasma. Nail erythrasma is a rare entity. Additionally, this case highlights a new clinical presentation of nail erythrasma as melanonychia.

Dermatologic Manifestations of the Lower Extremity: Nail Surgery

Nail surgery is a fundamental component of podiatric surgery. Nail disorders are common and may cause significant morbidity and occasionally mortality. Diagnosis of inflammatory and infectious conditions, and of benign or malignant tumors, often requires a biopsy of the nail unit. Excisional surgery may also be curative for certain tumors. This article reviews key elements of nail anatomy, surgical preparation, local anesthesia, and methods to achieve and maintain a bloodless field. A familiarity with these concepts should allow clinicians to develop a surgical plan and approach when patients present with a nail disorder requiring biopsy or surgical treatment.

Delayed Reconstruction for the Non-Amputative Treatment of Subungual Melanoma

BACKGROUND

In cases of early stage subungual melanoma (SUM), conservative treatment with non-amputative wide excision of the nail unit and subsequent skin graft is preferred over amputation to preserve the involved digit.

OBJECTIVE

We report a series of patients with SUM treated with conservative surgery and suggest an effective supplementary treatment process.

METHODS

We retrospectively reviewed 10 patients (2 males, 8 females) who were diagnosed with in situ or minimally invasive SUM on the first biopsy and underwent non-amputative wide excision of the nail unit. All patients underwent secondary intention healing during the histopathological re-evaluation of the entire excised lesion, and additional treatment was administered according to the final report.

RESULTS

In two of 10 patients, amputation was performed because of the detection of deep invasion (Breslow thickness: 4.0, 2.3 mm) from the final pathologic results, which differed from the initial biopsy. In six patients who received delayed skin graft, the mean total time required for complete healing after secondary intention healing and the skin graft was 66.83±15.09 days. As a result of this delayed skin graft, the final scarring was similar to the original shape of the nail unit, scored between 5 and 10 on a visual analogue scale. Most patients were satisfied with this conservative surgery except one patient, who had volar portion involvement and received an interpolated flap instead of a skin graft.

CONCLUSION

Our treatment process can reduce the risk of incomplete resection and improve cosmetic outcomes in patients with SUM.

Tips for diagnosis and treatment of nail pigmentation with practical algorithm

The observation of a black-brown pigmentation of the nail is often alarming for the patient and for the clinician, as they are aware that it can be a possible clinical manifestation of melanoma of the nail apparatus. Luckily, however, nail melanoma is a much less frequent cause of brown-black nail color than other melanocytic and nonmelanocytic pigmentations, which include subungual hematoma, exogenous pigmentations, and melanonychia due to benign conditions. A correct clinical history and careful examination help the clinician to distinguish the different conditions and to decide the correct management of melanonychia both in children and in adults.

Fungal Melanonychia

Melanonychia is characterized by tan, brown, or black pigmentation within the nail plate. Fungal melanonychia is rare and may simulate longitudinal melanonychia caused by melanocytic lesions. We report six cases of fungal melanonychia which were confirmed histopathologically or mycologically. On culture, Candida and/or Aspergillus species were isolated in four patients. The nail pigmentation improved after treatment with antifungal agents in all cases, but one patient experienced a new lesion on another nail after cessation of treatment. Fungal infection should be considered as a cause of melanonychia, and fungal melanonychia should be differentiated from the melanonychia caused by melanocytic lesions, particularly by subungual melanoma.

Nail histopathology

The structure of the nail unit is complex and many dermatologists and dermatopathologists have an incomplete understanding of it. Familiarity with the anatomy and histology of this unit, however, is a key factor in improving the diagnostic yield of nail biopsy. Inflammatory or infectious conditions that affect the nail can have a marked impact on a patient's quality of life. A wide-ranging variety of tumors can also develop in this region and they may be life-threatening or require surgery that will result in functional defects. The author reviews the anatomy and histology of the nail unit as well as the basic histopathologic findings in the most common conditions affecting the nails.

LONGITUDINAL MELANONYCHIA: DETECTION AND MANAGEMENT OF NAIL MELANOMA

Malignant melanoma of the nail confers a higher mortality rate compared to other cutaneous melanomas, which is often attributable to delayed diagnosis. Two-thirds of nail melanomas present as longitudinal melanonychia (LM), longitudinally-oriented brown-black bands of pigment in the nail plate. This article delineates the appropriate clinical approach toward evaluation and management of a patient with longitudinal melanonychia, which includes determining risk factors for melanoma, recognizing scenarios in which biopsy is indicated, selecting the appropriate biopsy technique, and managing a patient in whom the diagnosis of nail melanoma has been made.

Laugier-Hunziker syndrome: a report of three cases and literature review

Laugier–Hunziker syndrome (LHS) is an acquired pigmentary condition affecting lips, oral mucosa and acral area, frequently associated with longitudinal melanonychia. There is neither malignant predisposition nor underlying systemic abnormality associated with LHS. Herein, we present three uncommon cases of LHS with possibly new feature of nail pigmentation, which were diagnosed during the past 2 years. We also review the clinical and histological findings, differential diagnosis, and treatment of the syndrome in published literature.

Melanonychia

Melanonychia, or melanin-derived brown-to-black nail pigmentation, is a diagnostic challenge for clinicians. The most serious disease of the nail unit, melanoma, primarily presents with melanonychia. However, melanonychia most often occurs as a result of benign etiologies such as nail matrix melanocytic activation, nail matrix melanocytic hyperplasia, and nail invasion by melanin-producing pathogens. Regrettably, patients with nail apparatus melanoma are often initially misdiagnosed, and due to diagnostic delays of an average of 2 years, melanoma of the nail unit carries a poor prognosis. Having a thorough knowledge of the various causes of melanonychia and using a systematic approach when evaluating brown-to-black nail pigmentation may help prevent misdiagnosis and thereby improve prognosis.

Tangential Biopsy Thickness versus Lesion Depth in Longitudinal Melanonychia: A Pilot Study

Longitudinal melanonychia can be caused by melanocyte activation (hypermelanosis) or proliferation (lentigo, nevus or melanoma). Histopathologic examination is mandatory for suspicious cases of melanomas. Tangential biopsy of the matrix is an elegant technique avoiding nail plate dystrophy, but it was unknown whether the depth of the sample obtained by this method is adequate for histopathologic diagnosis. Twenty-two patients with longitudinal melanonychia striata were submitted to tangential matrix biopsies described by Haneke. The tissue was stained with hematoxylin-eosin and the specimens were measured at 3 distinct points according to the total thickness: largest (A), intermediate (B) and narrowest (C) then divided into 4 groups according to the histopathologic diagnosis (G1: hypermelanosis; G2: lentigos; G3: nevus; G4: melanoma). The lesions were measured using the same method. The mean specimen/lesion thickness measure values for each group was: G1: 0,59/0,10 mm, G2: 0,67/0,08 mm, G3: 0,52/0,05 mm, G4: 0,58/0,10 mm. The general average thickness for all the specimens/lesions was 0,59/0,08 mm. We concluded that the tangential excision, for longitudinal melanonychia, provides an adequate material for histopathological diagnosis.

Key point in dermoscopic differentiation between early nail apparatus melanoma and benign longitudinal melanonychia

Longitudinal melanonychia presents in various conditions including neoplastic and reactive disorders. It is much more frequently seen in non-Caucasians than Caucasians. While most cases of nail apparatus melanoma start as longitudinal melanonychia, melanocytic nevi of the nail apparatus also typically accompany longitudinal melanonychia. Identifying the suspicious longitudinal melanonychia is therefore an important task for dermatologists. Dermoscopy provides useful information for making this decision. The most suspicious dermoscopic feature of early nail apparatus melanoma is irregular lines on a brown background. Evaluation of the irregularity may be rather subjective, but through experience, dermatologists can improve their diagnostic skills of longitudinal melanonychia, including benign conditions showing regular lines. Other important dermoscopic features of early nail apparatus melanoma are micro-Hutchinson's sign, a wide pigmented band, and triangular pigmentation on the nail plate. Although there is as yet no solid evidence concerning the frequency of dermoscopic follow up, we recommend checking the suspicious longitudinal melanonychia every 6 months. Moreover, patients with longitudinal melanonychia should be asked to return to the clinic quickly if the lesion shows obvious changes. Diagnosis of amelanotic or hypomelanotic melanoma affecting the nail apparatus is also challenging, but melanoma should be highly suspected if remnants of melanin granules are detected dermoscopically.