Verrucous pseudonevoid melanoma

Verrucous-Keratotic Malignant Melanoma (VKMM)

We report a patient with a verrucous keratotic variant of melanoma visiting the policlinic of Medical Institute of Ministry of Interior (MVR-Sofia), Department of Dermatology and Dermatologic surgery, with a keratotic verrucous lesion, located on the right thigh, partially deeply pigmented at upper right quadrant. The lesion had appeared three years ago before her presentation in the policlinic, and it had gradually enlarged and become darker in the last twelve months. The surface of the lesion was covered with thick hyperkeratotic lobules. The histologic evaluation revealed verrucous melanoma with a tumour thickness of 3 mm and Clark Level IV and focal ulceration. The tumour was staged as stage IIB (T3bN0M0). Sentinel lymph node biopsy was planned. Verrucous-keratotic forms of malignant melanoma occur more commonly in women and favour the extremities, but may be found on any anatomic site. Seventy-one percent of this melanoma type are situated on the upper and lower extremities. Although two-thirds of these neoplasms can be can be histologically graded according to the classification of Clark, one-third of these melanomas with marked verrucous hyperplasia and hyperkeratosis of the epidermis do not fit into his classification. Histological classification of patients with a verrucous keratotic type of melanoma may sometimes be extremely difficult. The marked papilliferous architecture of these lesions made an assessment of Breslow depth difficult. The presented case highlights the clinical existence and features of such benign-looking melanomas. It is therefore important for surgical pathologists to recognise this unusual variant of malignant melanoma, as it may be confused both clinically and pathologically with benign lesions.

Morphological features of naevoid melanoma: results of a multicentre study of the International Dermoscopy Society

BACKGROUND

Naevoid melanoma (NeM), a rare variant of melanoma, can be difficult to detect as its clinical and histopathological morphology can simulate a naevus.

OBJECTIVES

To describe the clinical and dermoscopic features associated with NeM.

METHODS

Lesions with a histopathological diagnosis of NeM were collected via an e-mail request sent to all members of the International Dermoscopy Society. All lesions were histopathologically reviewed and only lesions fulfilling a set of predefined histopathological criteria were included in the study and analysed for their clinical and dermoscopic features.

RESULTS

Twenty-seven of 58 cases (47%) fulfilled the predefined histopathological criteria for NeM and were included in the study. Clinically, 16 of the 27 NeMs presented as a nodular lesion (59%), eight (30%) as plaque type and three (11%) as papular. Analysis of the global dermoscopic pattern identified three types of NeM. The first were naevus-like tumours (n = 13, 48%), typified by a papillomatous surface resembling a dermal naevus. In these lesions local dermoscopic features included irregular dots/globules (46%), multiple milia-like cysts (38%) and atypical vascular structures (46%). The second type were amelanotic tumours (n = 8, 30%), typified by an atypical vascular pattern (75%). The third type consisted of tumours displaying a multicomponent pattern (n = 4, 15%), characterized by classical local melanoma-specific criteria. Two lesions (7%) were classified as mixed-pattern tumours as they did not manifest any of the aforementioned patterns.

CONCLUSIONS

While NeMs may be clinically difficult to differentiate from naevi, any papillomatous lesion displaying dermoscopically atypical vessels and/or irregular dots/globules should prompt consideration for the possible diagnosis of NeM.

The pathology of melanoma

Although melanoma represents only 10% of all skin cancer diagnoses, it accounts for at least 65% of all skin cancer-related deaths. The number of new cutaneous melanoma cases projected during 2010 was 68,000-a 23% increase from the 2004 prediction of 55,100 cases. In 2015, the lifetime risk of developing melanoma is estimated to increase to 1 in 50. As the incidence of melanoma continues to rise, now more than ever, clinicians and histopathologists must have familiarity with the various clinical and pathologic features of cutaneous melanoma.

Spindle cell melanocytic lesions--part I: an approach to compound naevoidal pattern lesions with spindle cell morphology and Spitzoid pattern lesions

Melanocytic lesions show great morphological diversity in their architecture and the cytomorphological appearance of their composite cells. Whereas functional melanocytes reveal a dendritic cytomorphology and territorial isolation, lesional naevomelanocytes and melanoma cells typically show epithelioid, spindled or mixed cytomorphologies and a range of architectural arrangements. Spindling is common to melanocytic lesions, and may be either 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 because of 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 because of 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 can reliably be resolved with this standard approach, problem areas do exist and cause no end of grief to the surgical pathologist or dermatopathologist. In this review, the authors present their algorithmic approach to spindle cell melanocytic lesions and discuss each entity in turn, in order to (1) model a systematic approach to such lesions, and (2) provide familiarity with those melanocytic lesions that either typically or occasionally display a spindled cytomorphology.

Carcinoid-like pattern in melanoma: report of 4 cases

Cutaneous melanoma can produce a wide variety of unusual morphological appearances, sometimes mimicking other tumors. We report on 4 cases of melanoma with carcinoid-like features, namely, arrangement of neoplastic cells in trabecules, ribbons, pseudorosettes, rosettes, and/or small round islands. A total of 10 biopsies from 4 patients were available for a histopathological study comprising congenital nevus, a nodule that had developed in this nevus and its persistence/recurrence, 3 primary cutaneous lesions, 3 metastases, and a recurrent/persistent lesion. In 7 of these 10 lesions, the most characteristic finding was a distinctive arrangement of the neoplastic cells as trabecules, ribbons, pseudorosettes, rosettes, or small round insular islands, thus closely resembling cell arrangement in carcinoids of various organs. All these tumors were positive for melanocytic markers. No neuroendocrine differentiation was demonstrated immunohistochemically. We conclude that the carcinoid-like pattern in melanoma, namely, the pattern in which neoplastic cells are arranged in trabecules, ribbons, cords, rosettes, pseudorosettes, and small round insular nests resembling those in carcinoids, is a distinctive pattern, which may rarely occur in primary cutaneous melanoma, its recurrence or metastasis, or in a melanoma associated with a large congenital nevus. This morphological type of melanoma may produce a serious diagnostic pitfall, but despite a confusing microscopic appearance, these tumors seem to demonstrate a conventional immunohistochemical profile.

Medicolegal aspects of neoplastic dermatology

Medical malpractice litigation is rising at an explosive rate in the US and, to a lesser extent, in Canada. The impact of medical malpractice litigation on health care costs and the cost of insurance is dramatic. Certain specialist categories are becoming uninsurable in some parts of the US, while in others, clinicians are retiring early, restricting or changing practice or changing states of residence in consequence of medical malpractice claims and of the cost and availability of insurance. This, in turn, has had the real effect of denying care to patients in some communities in the US. Some 13% of all medical malpractice claims relate to one area of neoplastic dermatopathology, specifically, melanocytic neoplasia. Certain steps can be taken by pathology laboratories to reduce, but never completely eliminate, the risk of medical malpractice claims. In this review, attention is paid to the source of medical malpractice claims and an abbreviated approach to specific strategies for risk management is presented.

Unusual variants of malignant melanoma

A potential diagnostic pitfall in the histologic assessment of melanoma is the inability to recognize unusual melanoma variants. Of these, the more treacherous examples include the desmoplastic melanoma, the nevoid melanoma, the so-called 'minimal-deviation melanoma,' melanoma with prominent pigment synthesis or 'animal-type melanoma,' and the malignant blue nevus. Also problematic are the unusual phenotypic profiles seen in vertical growth phase melanomas; these include those tumors whose morphological peculiarities mimic cancers of nonmelanocytic lineage and those melanomas that express aberrant antigenic profiles not commonly associated with a melanocytic histogenesis. Metaplastic change in melanoma, balloon cell melanoma, signet-ring cell melanoma, myxoid melanoma, small cell melanoma and rhabdoid melanoma all have the potential to mimic metastatic and primary neoplasms of different lineage derivations. Abnormal immunohistochemical expression of CD 34, cytokeratins, epithelial membrane antigen, and smooth muscle markers as well as the deficient expression of S100 protein and melanocyte lineage-specific markers such as GP100 protein (ie HMB-45 antibody) and A103 (ie Melan-A) also present confusing diagnostic challenges. In this review, we will discuss in some detail certain of these novel clinicopathologic types of melanoma, as well as the abnormal phenotypic expressions seen in vertical growth phase melanoma.

My approach to atypical melanocytic lesions

Histological assessment of melanocytic naevi constitutes a substantial proportion of a dermatopathologist's daily workload. Although they may be excised for cosmetic reasons, most lesions encountered are clinically atypical and are biopsied or excised to exclude melanoma. Although dysplastic naevi are most often encountered, cytological atypia may be a feature of several other melanocytic lesions, including genital type naevi, acral naevi, recurrent naevi, and neonatal or childhood naevi. With greater emphasis being given to cosmetic results, and because of an ever increasing workload, several "quicker and less traumatising" techniques have been introduced in the treatment and diagnosis of atypical naevi including punch, shave, and scoop shave biopsies. A major limitation to all of these alternatives is that often only part of the lesion is available for histological assessment and therefore all too frequently the pathologist's report includes a recommendation for complete excision so that the residual lesion can be studied. Complete or large excision of all clinically atypical naevi permits histological assessment of the entire lesion, and in most cases spares the patient the need for further surgical intervention.

Morphological analysis of nevoid melanoma: a study of 20 cases with a review of the literature

Nevoid melanoma is a rare variant of melanoma characterized by deceptive morphologic features reminiscent of a benign melanocytic nevus. Twenty (13 nodular, 7 verrucous) nevoid melanomas were reviewed with the goal of identifying the predominant architectural patterns, cytologic features, and prognostic indicators. Although at scanning magnification, many lesions showed a strong resemblance to banal compound or dermal nevi, careful inspection in all cases demonstrated subtle pleomorphism and impaired maturation with depth, invariably accompanied by multiple dermal mitoses. Four tumors recurred and three metastasized, with subsequent death of the patients. Follow-up information for a period of at least 3 years was available in eight cases. In this group, mortality was 37.5%, the metastasis rate was 37.5%, and the local recurrence rate was 75%, with an average tumor thickness of 2.5 mm. We conclude that nevoid melanoma may be distinguished from a benign melanocytic nevus by a high index of suspicion, a careful analysis of architecture, and attention to cytologic features. Our data and a review of the literature do not support the notion that nevoid melanoma has a better prognosis than ordinary melanoma.

Minimal deviation and/or naevoid melanoma: is recognition worthwhile? A clinicopathological study of nine cases

One to two per cent of primary cutaneous melanomas share clinical features with benign melanocytic and non-melanocytic skin lesions, and even at histology recognition of their malignant nature is problematic, mainly due to the lack of an intraepithelial component, their nodular aspect and the monotonous cell population throughout the lesion. These tumours were termed minimal deviation melanomas (MDMs) by Reed et al. and later naevoid melanomas by Schmoeckel et al. The name MDM suggests the concept of a more favourable outcome for these melanomas that do not (yet) show the typical features of fully evolved lesions able to metastasize, although naevoid melanomas seem to behave like 'common' melanomas. In a retrospective analysis of nine cases of MDM collected from our database and followed for a median duration of 112 months, we faced similar clinical and histological pitfalls and observed local recurrence following marginal resection. Wide excision, even of local recurrence, and therapeutic node dissection could nevertheless provide survival comparable at least to that predicted by mathematical models for patients who initially had optimal treatment.

Small cell malignant melanoma: a variant of naevoid melanoma. Clinicopathological features and histological differential diagnosis

AIMS

To describe the clinical and histopathological features of a rare variant of naevoid melanoma, small cell melanoma, and discuss the histological differential diagnoses.

METHODS

The clinical and histological features of cases of malignant melanoma with the histological features of small (non-Merkel like) melanoma were reviewed and documented. In addition, five cases had available material for immunohistochemistry and this was performed using antibodies to the S100 protein and melan-A, and the HMB-45 antibody.

RESULTS

There were 15 cases of small cell melanoma from 14 (10 female, four male) patients, aged between 30 and 77 (mean, 48.6) years. The trunk was the most common location. In more than half the cases, the provisional diagnosis was melanoma/borderline lesion. All shared similar histological appearances of an intraepidermal component of in situ melanoma and a dermal component of nests of cells with hyperchromatic nuclei and scanty cytoplasm, usually in tightly packed nests. All components (junctional and intradermal) of the lesions investigated by immunohistochemistry were positive both for S100 protein and melan-A. All junctional components were positive with HMB-45, but with variable staining of the dermal components with this antibody.

CONCLUSIONS

Small cell malignant melanoma is postulated to be a distinct histopathological entity and a rare variant of naevoid melanoma. Such lesions can be difficult to interpret and easily missed at scanning magnification because the cells of the dermal component mimic benign naevus cells.

Pathology of malignant melanoma

This article describes the histopathologic and clinical appearance of benign simulators of melanoma, radial and vertical growth phase malignant melanoma, and unusual variants of melanoma. Microstaging and prognostic parameters also are discussed.

Cutaneous melanoma and atypical Spitz tumors in childhood

BACKGROUND

Malignant melanoma in childhood is rare. As a result, the biology and natural history of melanoma in this age group is still poorly understood. Although the majority of Spitz nevi are benign regardless of atypical features, a particular problem is the continued confusion of Spitz nevi with atypical features with melanoma and the lack of specific criteria for their distinction. The latter discrimination is perhaps not so difficult when Spitz nevi are minimally atypical; however, the greater the atypia, the more challenging is this discrimination.

METHODS

All cases of malignant melanoma referred to Children's Hospital (Boston, MA) and to one of the authors were examined during the period of 1959-1995. Criteria for inclusion in the study included: (1) age up to 15 years; (2) availability of microscopic slides; and (3) availability of demographic data.

RESULTS

There were 11 males and 12 females, ranging in age from 2 to 15 years (mean age, 9.4 years). Histopathologically, the 23 tumors were categorized into four subgroups: (1) small cell melanoma (5); (2) adult-like melanoma (6); (3) Spitz-like melanoma (3), and (4) atypical Spitz tumors (9). The small cell melanomas were notable for localization to the scalp, significant thickness, and fatal outcome. The adult-like melanomas resembled typical tumors occurring in adults. The one fatal Spitz-like melanoma was located on the neck of a 14-year-old male. Two tumors in this group metastasized to regional lymph nodes, but were not associated with further aggressive disease on follow-up despite treatment with surgical excision only. The atypical Spitz tumors were characterized by significant thickness and abnormal features including prominent cellularity and mitotic activity.

CONCLUSIONS

Anatomic site and cell type may be important prognostic factors in addition to tumor thickness for childhood melanoma, but these tumors require further study. In addition, the biologic potential of atypical Spitz tumors has not been characterized sufficiently.

Verrucous naevoid and keratotic malignant melanoma: a clinico-pathological study of 20 cases

Verrucous naevoid malignant melanoma is a recently described variant of malignant melanoma that may be confused both clinically and histologically with benign lesions. This study reports the clinical and pathological features of 20 such cases. These constituted 3.2% of all melanomas diagnosed in the Department of Pathology, Aberdeen University, in the period 1970-1991. They occurred more often on the back and limbs of male patients with a mean age of 57 years. Clinical diagnosis of benign lesions (warty naevi, papillomas, seborrhoeic keratosis and cysts) were made in over 50% of the cases. Eight patients had metastases, seven of whom died of their disease. Microscopically, these lesions exhibited a spectrum of naevoid features such as symmetry, exophytic and papilliferous growth pattern, hyperkeratosis and pseudo-epitheliomatous hyperplasia. The majority, however, showed lateral intra-epidermal spread and were composed of large epithelioid cells exhibiting various degrees of cellular pleomorphism. Histological classification was difficult, as more than 50% of the cases were initially labelled unclassifiable. The marked papilliferous architecture of these lesions made assessment of Breslow depth and Clark levels difficult. Initially, 10% of the cases were histologically diagnosed as benign. It is therefore important for surgical pathologists to recognize this unusual variant of malignant melanoma, as it may be confused both clinically and pathologically with benign lesions.

Multiple agminated pigmented Spitz nevi (mimicking acral lentiginous malignant melanoma and dysplastic nevus) in an African-American girl

BACKGROUND

Reed's nevi are distinguished from Sptiz tumors by their significant melanogenesis and growth pattern. They may be confused with melanoma on clinical and histologic grounds.

CASE REPORT

An unusual case in which multiple agminated Reed's nevi mimicked acral lentiginous malignant melanoma in an African-American girl is presented. A critical review of the literature is presented to assist in the diagnosis.

CONCLUSIONS

Awareness of this entity and of its possible clinical presentations and judicious application of conventional hematoxylin-eosin microscopic criteria remain the most useful methods to bring the correct diagnosis in most instances. Mutilating or excessive surgery may be avoided for most cases of pigmented spindle and epithelioid cell nevus.