Expression of proliferating cell nuclear antigen in Spitz nevus

Immunohistologic Evaluation of Putatively Mutant p53 Protein in Cutaneous Melanocytic Neoplasms

Mutations in the p53 tumor suppressor gene, located at chromosomal locus 17pI3, are the most commonly seen genetic alterations found in human malignancies. Their role in the pathogenesis of malignant melanoma is thought to be limited, although variable results have been reported in reference to immunoreactivity for putatively mutant p53 protein (mp53) in melanocytic lesions in general. In that light, the authors undertook an immunohistologic evaluation of 256 well-characterized tumors in that category, including common nevi (CN; n=73); Spitz nevi (SN; n=40); nodular melanomas (NMMs; n=32), superficial spreading melanomas (SMMs; n=65); lentigo maligna melanomas (LMMs; n=23); and melanomas arising in preexisting nevi (MANs; n=23). One hundred cells were counted manually in randomly selected high-power microscopic fields, in regard to nuclear labeling for mp53. Results were recorded semiquantitatively, as negative, positive (1-4% of tumor cells); and positive (>5% of tumor cells). No examples of CN or SN demonstrated any immunoreactivity whatever for mp53, whereas 105 of 143 melanomas (73%) did so. However, an mp53 index of >50% was seen in only 29% of the latter lesions. NMMs were most often mp53-positive and showed the highest numerical level of nuclear labeling, followed in respective order by SMMs, and LMMs/MANs. These results suggest that negative mp53-immunostaining cannot be equated with the diagnostic interpretation of a benign melanocytic neoplasm, because 27% of melanomas also failed to label for that determinant. However, the presence of mp53-immunolabeling in a melanocytic proliferation-even if at low levels-should conversely prompt careful consideration of melanoma as the favored diagnosis in the confined setting of morphologically difficult cases, inasmuch as no example of CN or SN in this series had that characteristic.

Atypical Spitzoid neoplasms: a review of potential markers of biological behavior including sentinel node biopsy

Atypical cutaneous melanocytic lesions, including those with Spitzoid features, can be difficult to categorize as benign or malignant. This can lead to suboptimal management, with potential adverse patient outcomes. Recent studies have enhanced knowledge of the molecular and genetic biology of these lesions and, combined with clinicopathological findings, is further defining their biological spectrum, classification, and behavior. Sentinel node biopsy provides important prognostic information in patients with cutaneous melanoma, but its role in the management of melanocytic lesions of uncertain malignant potential (MELTUMP) is controversial. This paper examines the role of molecular testing and sentinel node biopsy in MELTUMPs, particularly atypical Spitzoid tumors.

The molecular basis of melanomagenesis and the metastatic phenotype

The last two decades have seen spectacular advances in our understanding of the biology of melanoma and, in particular, have elucidated the mechanisms operative in disease initiation and progression. With respect to the former, the genetics of melanoma and in particular the impact of genetic defects on dysregulation of the cell cycle are key issues in malignant transformation and are a major focus of this review. With respect to the latter, consideration also is given to the acquisition of growth factor autonomy and the capacity for invasion and metastasis from the standpoint of cell adhesion, motility, and matrix digestion. These events have specific morphologic correlates that will be briefly addressed. Where relevant, we will address certain of the modern pharmacogenetic strategies that flow from these novel observations concerning melanoma biology.

Prognosticators of melanoma, the melanoma report, and the sentinel lymph node

Since the 1960s, the clinical characteristics of melanoma, its histopathology and its biological basis have been the subject of intense study at pigmented lesion clinics in North America, Europe, and Australia. More recently, the immense database of the Melanoma Committee of the American Joint Committee on Cancer (AJCC) has been exploited through complex mathematical models to measure the impact of various histologic features of primary melanomas and of sentinel lymph node deposits and to correlate these parameters with patient survival. The wealth of modern information available to pathologists and clinicians has become of vital interest to the prognostication of the individual patient with melanoma. The purpose of this review is to bring to the attention of anatomic pathologists the essential characteristics of the pathology report for primary cutaneous melanoma in the modern era.

Proliferation, apoptosis, and survivin expression in a spectrum of melanocytic nevi

BACKGROUND

Apoptosis is important for maintenance of tissue homeostasis and often dysregulated in cutaneous neoplasms. The apoptosis inhibitor survivin is expressed in melanoma and non-melanoma skin cancers and benign keratinocytic lesions. Its expression has not been studied in melanocytic nevi.

OBJECTIVE

We determined the expression pattern of survivin in benign melanocytic nevi in comparison to markers of proliferation and apoptosis.

METHODS

Six cases of each of the following melanocytic nevi were retrieved from a dermatopathology archive: compound dysplastic nevus, intradermal nevus, compound nevus, neurotized intradermal nevus, and Spitz nevus. Survivin expression was evaluated by in situ hybridization. Apoptotic and proliferation indices were calculated by counting immunoreactive cells in terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling and proliferating cell nuclear antigen immunostained sections, respectively.

RESULTS

All nevi, regardless of histologic type, expressed survivin. Compound melanocytic lesions expressed survivin in both epidermal and dermal compartments. The apoptotic rate was low for dysplastic, compound, and Spitz nevi, and apoptotic cells were not identified in any neurotized nevus. The proliferative index was highest for Spitz nevi, while all other nevi demonstrated rare positive cells.

CONCLUSIONS

Survivin is consistently expressed in benign melanocytic lesions, while apoptotic cells are rarely identified, suggesting the dysregulation of apoptotic pathways with the accumulation of cells in these neoplasms.

S100A6 protein expression is different in Spitz nevi and melanomas

The Spitz nevus is a benign melanocytic lesion that can be identified reliably in many cases by conventional histopathological criteria. However, there are subsets of Spitz nevi and of malignant melanoma that closely resemble each other and represent diagnostic challenges. S100 proteins are of interest because of their involvement in neoplastic processes and their genes are clustered in chromosome 1q21. Chromosome 1 contains mutations in several types of tumors, including melanomas. The expression of different S100 proteins (A2, A6 and A8/A9 or A12) was examined in 42 Spitz nevi, 105 melanomas, and 73 melanocytic nevi to test the hypothesis that their expression differs among these entities and may contribute to the distinction between these entities. The results showed an up-regulation of S100A6 protein in Spitz nevi, melanomas, and melanocytic nevi but with a different percentage of positivity and pattern of immunoreactivity. The differences between these three entities were statistically significant (P <.001). All 42 Spitz nevi (100%) showed strong and diffuse S100A6 protein expression, both in junctional and in dermal components of the nevi. Thirty-three percent of melanomas expressed S100A6 (35/105). The expression was mainly weak (30/35) and patchy in the dermal component and was negative or minimal in the junctional component. Fifty-six percent of different subtypes of melanocytic nevi (41/73) expressed S100A6, almost all of them weakly (40/41) and in the dermal component. Normal intraepidermal melanocytes were negative. The melanocytic cells in these three entities did not express S100A2, S100A8/A9 or A12. However, an up-regulation of S100A2 and S100A8/A9 or A12 proteins was observed in normal keratinocytes in the epidermis overlying Spitz nevi and melanomas, without differences. In summary, a simple immunohistochemical test for S100A6 protein differentiated between Spitz nevi, melanomas, and melanocytic nevi. This marker could be used when the distinction is very difficult or controversial in routine studies, especially when there is a junctional component. Further molecular analyses of the S100A6 protein and gene should be performed to study the underlying genetic bases for such differences.

Immunohistochemical markers of melanocytic lesions: a review of their diagnostic usefulness

We critically reviewed recent literature reports of 25 melanocytic immunohistochemical markers. This review organizes and summarizes the many new studies of old and novel melanocytic markers and identifies the most promising diagnostic immunohistochemical markers that can be used to distinguish melanocytic from nonmelanocytic lesions and benign melanocytic from malignant melanocytic lesions.

Sentinel lymph node biopsy in patients with diagnostically controversial spitzoid melanocytic tumors

Melanomas can be difficult to diagnose histologically if they deviate in their growth pattern or cytology only minimally from a nevus. On occasion, even experts on melanocytic lesions may not reach a consensus on whether a lesion is a benign but unusual nevus or a malignant melanoma mimicking a nevus. This diagnostic dilemma is particularly well known for the distinction of Spitz nevus from melanoma. Diagnostic uncertainty and disagreement among consultant pathologists lead to confusion about the prognosis and clinical management of patients. In this study we present the clinical and pathologic findings of 10 patients with diagnostically controversial melanocytic tumors, who underwent sentinel lymph node biopsy. In all of these cases, the diagnostic controversy among experts was between Spitz nevus and melanoma. Seven patients were female, and three were male, ranging in age from 7 to 46 years (mean 21 years). Histologic examination of the sentinel lymph nodes revealed tumor deposits in the lymph node parenchyma in 5 of 10 patients. Among patients with positive sentinel lymph nodes, two had satellite nodules and one showed additional tumor deposits in three nonsentinel regional lymph nodes. All patients are alive and free of disease with a follow-up of 10-54 months (mean 34 months). Our study illustrates the role of a sentinel lymph node biopsy in the evaluation of patients with diagnostically controversial melanocytic tumors. Although the presence of metastatic tumor deposits in the sentinel lymph node supports the diagnosis of malignant melanoma, further studies are needed to determine the prognostic significance of the sentinel lymph node findings in such patients.

MIB-1 monoclonal antibody to determine proliferative activity of Ki-67 antigen as an adjunct to the histopathologic differential diagnosis of Spitz nevi

BACKGROUND

The histopathologic differential diagnosis of Spitz nevus (SN) from malignant melanoma (MM) may be difficult.

OBJECTIVE

Our purpose was to determine the staining pattern and usefulness of MIB-1 antibody, which recognizes Ki-67 antigen in formalin-fixed, paraffin-embedded tissue, as an adjunct to the histopathologic differential diagnosis of SN.

METHODS

Twenty-five compound SNs, 27 MMs, and 26 compound nondysplastic melanocytic nevi (MNs) were immunostained with the MIB-1 antibody.

RESULTS

The mean counts of MIB-1--stained tumor cells of the epidermal and dermal components, both alone and together, were significantly lower in SNs and MNs than in MMs (P <.0001). The dermal counts showed the best discriminating power. In addition, the mean dermal/epidermal count ratios for MIB-1 in SNs and MNs (0.25 and 0.23, respectively) were significantly lower than the corresponding ratio (0.94) in MMs (P <.0001).

CONCLUSION

MIB-1-stained tumor cell counts, especially of the dermal component, and dermal/epidermal MIB-1 count ratios may be helpful as an adjunct to the histopathologic differential diagnosis of SN.

Concurrent Ki-67 and p53 immunolabeling in cutaneous melanocytic neoplasms: an adjunct for recognition of the vertical growth phase in malignant melanomas?

Ki-67 labeling of paraffin sections has been correlated with the number of cells in non-G(o) phases of the replicative cell cycle, and this immunohistochemical technique has been applied to the evaluation of a variety of human neoplasms. Similarly, immunolabeling for p53 protein has been used to detect mutations in the corresponding gene, as a reflection of possible cellular transformation in the same context. Both of these techniques were applied to 253 melanocytic tumors of the skin to assess their possible utility in the diagnosis and subcategorization of such lesions. They included 76 banal (common) nevi (CN), 39 Spitz nevi (SN), 62 superficial spreading malignant melanomas in radial growth (SSMMs), 32 nodular malignant melanomas (NMMs), 21 lentigo maligna melanomas in radial growth (LMMs), and 23 melanomas arising in association with preexisting compound nevi (MCN). One hundred cells were counted randomly in each tumor, and dark, exclusively nuclear reactivity was scored as positive labeling; results were recorded as percentages. Negligible Ki-67 and p53 labeling was seen in CN and SN, at a level that was similar to that obtained in cases of LMM and MCN. The largest proportion of Ki-67-positive and p53-positive cells was observed in NMMs, followed by SSMMs. Radial growth-phase SSMMs and LMMs demonstrated immunoprofiles that were similar to those of melanocytic nevi, and MCN did so as well. The prototypical malignant melanocytic tumor representing the vertical growth phase-nodular melanoma--demonstrated a statistically significant difference from all other lesions in this study with respect to Ki-67 index (P = .008, chi2) and p53 reactivity (P < .000001, chi2). Subsequent concurrent use of a Ki-67 threshold index of 10% and a p53 index of 5% correctly indicated the presence of vertical growth in 75% of NMMs, whereas only 8% of radial growth phase melanomas of other types were colabeled at the same levels of reactivity for the two markers (P < .00001, chi2). Thus, although the distinction between benign and malignant melanocytic tumors could and should not be based on immunohistology for Ki-67 and p53, these results suggest that the latter determinants may, in fact, be used as an adjunct to morphology in the recognition of the vertical growth phase in cutaneous malignant melanomas.

Spitz nevus or melanoma?

Spitz nevi are benign melanocytic neoplasms of children and young adults that can be exceedingly difficult to distinguish from malignant melanomas. Although a nearly definite diagnosis can be made in most cases, the histological distinction between Spitz nevi and melanomas is equivocal in about 6% to 8% of cases. In those cases, and perhaps even with presumed benign Spitz nevi, clear surgical margins are desirable. The most helpful differentiating features of Spitz nevi are patient age, sharp demarcation, symmetry, maturation of melanocytes at the base, and epithelial hyperplasia. None of these criteria are completely reliable, and multiple other criteria must be considered as well.

Mitotic cyclins and cyclin-dependent kinases in melanocytic lesions

Recent evidence has implicated cyclins and cyclin-dependent kinases in the evolution and progression of various malignancies. We studied the immunohistochemical expression of cyclin A, cyclin B, and cyclin-dependent kinase p34cdc2 in a broad spectrum of benign and malignant melanocytic lesions. Formalin-embedded, parrafin-fixed tissue sections from 66 malignant melanomas (MM) and 60 benign nevi were examined for the expression of these cell-cycle proteins. The results were compared with the standard proliferative marker Ki-67 and mitotic index. MM showed significantly higher immunoreactivity for cyclin A, cyclin B, p34cdc2, and Ki-67 compared with benign nevi. Cyclin A, p34cdc2, and Ki-67 displayed strong co-expression in MM. Overexpression of cyclin A and p34cdc2 correlated with histological type, mitotic activity, Ki-67 index, tumor thickness, Clark's level, and clinical outcome in MM. In invasive MM, increased immunostaining of cyclin A and Ki-67 were associated with decreased patient survival. These findings indicate potential roles of mitotic cyclins and cyclin-dependent kinases in the pathogenesis and progression of malignant melanoma.

Dermatopathologic variants of malignant melanoma

An appropriate biopsy is the pivotal procedure that facilitates accurate histopathologic diagnosis of a pigmented skin lesion. Excisional skin biopsy is the method of choice for removing a suspected malignant melanoma. More than 95% of malignant melanomas that involve the skin belong to one of the four most common clinicopathologic categories: superficial spreading, nodular, lentigo maligna, and acral lentiginous melanoma. A small but important group of cutaneous melanomas can be classified as unusual variants. Many of these unusual variants have a distinct histopathologic appearance; they include desmoplastic melanoma, neurotropic melanoma, pedunculated melanoma, metastatic melanoma, amelanotic melanoma, melanoma arising within a benign nevus, regressing ("invisible") melanoma, and balloon cell melanoma. Other lesions may simulate malignant melanoma histopathologically. Immunohistochemical stains, such as S-100 protein, vimentin, keratin, and HMB-45, are useful for distinguishing these lesions from true melanoma.