Dermal Melanocytic Nevi Research Articles

Cd34+ Stromal Cells/Telocytes in Normal and Pathological Skin.

We studied CD34+ stromal cells/telocytes (CD34+SCs/TCs) in pathologic skin, after briefly examining them in normal conditions. We confirm previous studies by other authors in the normal dermis regarding CD34+SC/TC characteristics and distribution around vessels, nerves and cutaneous annexes, highlighting their practical absence in the papillary dermis and presence in the bulge region of perifollicular groups of very small CD34+ stromal cells. In non-tumoral skin pathology, we studied examples of the principal histologic patterns in which CD34+SCs/TCs have (1) a fundamental pathophysiological role, including (a) fibrosing/sclerosing diseases, such as systemic sclerosis, with loss of CD34+SCs/TCs and presence of stromal cells co-expressing CD34 and αSMA, and (b) metabolic degenerative processes, including basophilic degeneration of collagen, with stromal cells/telocytes in close association with degenerative fibrils, and cutaneous myxoid cysts with spindle-shaped, stellate and bulky vacuolated CD34+ stromal cells, and (2) a secondary reactive role, encompassing dermatitis—e.g., interface (erythema multiforme), acantholytic (pemphigus, Hailey–Hailey disease), lichenoid (lichen planus), subepidermal vesicular (bullous pemphigoid), psoriasiform (psoriasis), granulomatous (granuloma annulare)—vasculitis (leukocytoclastic and lymphocytic vasculitis), folliculitis, perifolliculitis and inflammation of the sweat and sebaceous glands (perifolliculitis and rosacea) and infectious dermatitis (verruca vulgaris). In skin tumor and tumor-like conditions, we studied examples of those in which CD34+ stromal cells are (1) the neoplastic component (dermatofibrosarcoma protuberans, sclerotic fibroma and solitary fibrous tumor), (2) a neoplastic component with varying presentation (fibroepithelial polyp and superficial myxofibrosarcoma) and (3) a reactive component in other tumor/tumor-like cell lines, such as those deriving from vessel periendothelial cells (myopericytoma), epithelial cells (trichoepithelioma, nevus sebaceous of Jadassohn and seborrheic keratosis), Merkel cells (Merkel cell carcinoma), melanocytes (dermal melanocytic nevi) and Schwann cells (neurofibroma and granular cell tumor).

Beneficial Effects of Treatment With Low-Fluence 755-nm Q-Switched Alexandrite Laser for Nevus of Ota.

Nevus of Ota is a benign dermal and mucosal melanocytic nevus that can be cured by Q-switched lasers. However, the incidence rate of post-treatment hyperpigmentation in Asian patients remains high. Low-fluence Q-switched Nd:YAG laser (QSNY) has been proved effective in the early treatment of nevus of Ota. Q-switched alexandrite laser (QSAL) was found to achieve a higher successrate and lower complication rate than QSNY. This study aims to evaluate the efficacy and safety of low-fluence 755 nm QSAL in the treatment of nevus of Ota. A total of 81 patients with nevus of Ota were retrospectively evaluated. Among them, 39 went through the high-fluence QSAL (3 mm spot, 5.0-8.0 J/cm2 ) and 42 were treated by low-fluence QSAL (5 mm spot, 2.2-2.8 J/cm2 ). Treatments were given every 6 months three times. Standard photos of the lesions were taken to evaluate the efficacy. All adverse events were noted. The low-fluence QSAL group achieved a significantly higher mean efficacy score than the high-fluence QSAL group after the first treatment (3.62 ± 0.85 vs. 2.9 ± 0.79, P < 0.001) and at the final follow-up visit (4.52 ± 0.63 vs. 4.03 ± 0.96, P < 0.05). Post-inflammation hyperpigmentation rate was significantly lower in the low-fluence QSAL group than in the high-fluence QSAL group (4.8% vs. 25.6%, P < 0.001). No patient reported hyperkeratosis, scarring, bleeding, skin textural change, or recurrence at the final visit in either group. The low-fluence QSAL is more effective and safer than the traditional high-fluence QSAL because of its better clinical outcome and lower complication rate in the treatment of nevus of Ota. Lasers Surg. Med. © 2021 Wiley Periodicals LLC.

Melanoma in the setting of nevus of Ota: a review for dermatologists.

Nevus of Ota, also known as oculodermal melanocytosis or nevus fuscoceruleus ophthalmomaxillaris, is a benign dermal melanocytic nevus that most commonly affects Asian women. While the lesion is largely a cosmetic concern, it has the potential to undergo malignant transformation to melanoma. Patients with nevus of Ota often present to a dermatologist at some point for examination or removal with laser therapy. Therefore, it is important for dermatologists to understand the cutaneous and extracutaneous risks these lesions carry and how they may present to further optimize management and appropriate referrals. This review describes the demographic, clinical, and prognostic features of melanoma in the setting of nevus of Ota, divided by the nature of the primary melanoma: cutaneous, orbital, intracranial.

Unexpected High Levels of BRN2/POU3F2 Expression in Human Dermal Melanocytic Nevi

Malignant melanoma is the most aggressive skin cancer. A majority of cancer-associated deaths are due to the invasion of cancer cells to distant tissues. Thus, it is of great importance to understand the mechanisms of metastatic spread. A potential marker for this is BRN2, encoded by the POU3F2 gene, that interacts with SOX transcription factors (Cook and Sturm, 2008; Malik et al., 2018). While some studies consider BRN2 as a positive regulator of microphthalmia-associated transcription factor (MITF), which favors proliferation (Goodall et al., 2004a; Wellbrock et al., 2008), other studies propose a dual function for BRN2 in both tumor proliferation and invasion, which could be controlled via the upregulation or downregulation of MITF, respectively (Simmons et al., 2017; Wellbrock and Arozarena, 2015).

A Rare Intraoral Manifestation of Nevus Ota - A Case Report

Nevus of Ota is a dermal melanocytic nevus which is characterized by benign hamartomatous hyperpigmentation clinically presented as a congenital or acquired blue or gray patch on the face, distributed on the ophthalmic and maxillary branches of the trigeminal nerve, found mostly in the Japanese people and is rare in the Indian subcontinent. It affects only 0.014%–0.034% of the Asian population and is found to be rare among the male population with male to female ratio of 1.4:8. The involvement of pigmentation over the pinna of the ear and oral mucosa is extremely rare and very few cases have been reported in literature. The case reported here is a case of Nevus of Ota with a rare intra oral finding in the hard palate.

Lasers and nevus of Ota: a comprehensive review

Nevus of Ota is a benign dermal melanocytic nevus that typically affects Asian children and women. The nevus presents as unilateral blue-gray hyperpigmented macules and patches scattered along the first and second divisions of the trigeminal nerve. Individuals with nevus of Ota experience emotional and psychosocial distress related to cosmetic disfigurement and often look for treatment options. Unfortunately, even when treated early, lesions of nevus of Ota are still difficult to treat. The use of lasers for the treatment of nevus of Ota lesions has become helpful in the management of dermal nevi. Currently, Q-switched (QS) lasers have been the most studied and demonstrated positive results for treatment of nevus of Ota. The purpose of this review article is to summarize the clinical efficacy and side effects associated with QS lasers and the treatment of nevus of Ota lesions.

Lymph Node Melanosis From a Primary Cutaneous Lesion Combining a Nodular (Tumoral) Melanosis and a Congenital Dermal Melanocytic Nevus

Tumoral or nodular melanosis is considered as a rare manifestation of a completely regressed melanoma whose histopathological features include confluent dermal nodular aggregates of heavily melanized polygonal cells consistent with melanophages. Tumoral melanosis involving also lymph node is an even rarer event that has been reported only twice in the literature. We report a case of lymph node melanosis in the sentinel lymph node draining from a primary cutaneous lesion combining a dermal tumoral melanosis consistent with a complete regressed melanoma associated with a residual part of a deep congenital nevus. We discuss the histopathological diagnosis of our primary cutaneous lesion and the sentinel lymph node microscopic findings, compare our case with the previous ones, and discuss the possible prognostic and therapeutic implications.

Clefts in dermal melanocytic nevi

International Journal of DermatologyVolume 50, Issue 11 p. 1387-1392 Morphology Clefts in dermal melanocytic nevi Eva-Maria Dutz MD, Eva-Maria Dutz MD Department of Dermatology and Allergology Biederstein, Technical University Munich, Munich, GermanySearch for more papers by this authorMarkus Braun-Falco MD, Markus Braun-Falco MD Department of Dermatology, Ludwig-Maximilian University Munich, Munich, GermanySearch for more papers by this author Eva-Maria Dutz MD, Eva-Maria Dutz MD Department of Dermatology and Allergology Biederstein, Technical University Munich, Munich, GermanySearch for more papers by this authorMarkus Braun-Falco MD, Markus Braun-Falco MD Department of Dermatology, Ludwig-Maximilian University Munich, Munich, GermanySearch for more papers by this author First published: 18 October 2011 https://doi.org/10.1111/j.1365-4632.2011.05084.x Dr Markus Braun-Falco, mdDepartment of DermatologyLudwig-Maximilian University MunichFrauenlobstr 9-1180337 MünchenGermanyE-mail: [email protected] Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Volume50, Issue11November 2011Pages 1387-1392 RelatedInformation

Nevus of Ota with Rare Palatal Involvement: A Case Report with Emphasis on Differential Diagnosis

Nevus of Ota, a dermal melanocytic nevus, is rare in the Indian subcontinent. It presents as a brown, blue, or gray patch on the face and is within the distribution of the ophthalmic and maxillary branches of the trigeminal nerve. The oral cavity is infrequently involved in nevus of Ota. Only 11 cases have been documented in the English literature. We report a rare case of intraoral nevus of Ota in a 22-year-old male patient. This paper focuses on the differential diagnosis of oral manifestations of nevus of Ota to assist in proper followup to avert malignant transformation.

Angiomatoid Intradermal Melanocytic Nevus or Chimeric Nevus?: A Potential Diagnostic Pitfall

Angiomatoid Intradermal Melanocytic Nevus or Chimeric Nevus?: A Potential Diagnostic Pitfall

Neurotized nevi of the oral mucosa: an immunohistochemical and ultrastructural analysis of nevic corpuscles

Nevic corpuscle (NC), a stacked lamellar structure reminiscent of Meissner corpuscle, is frequently observed in dermal melanocytic nevi. Although the heading 'neurotized' is classically used for these nevi, the exact neural nature of NC has been a topic of considerable debate. Neurotized nevi have received little attention in the dental literature, and there was no information on NC in oral melanocytic nevi. Six cases of oral intramucosal nevi with a significant number of NC (two completely and four partially neurotized nevi) were examined immunohistochemically and ultrastructurally. NC was composed of closely piled laminar cells devoid of visible melanin. NC and associated spindle nevus cells were immunopositive for S-100 protein but negative for HMB-45, myelin basic protein and epithelial membrane antigen. Within NC, no reactivity for neurofilament protein, protein gene product 9.5 or peripherin was evident. Numerous CD34-positive dendritic cells were located between nevus cells and often encircled NC. Ultrastructurally, NC consisted of concentrically layered elongated cells with a slender lamellated cytoplasm rich in thin filaments and pinocytotic vesicles. Their cytoplasmic processes were focally covered by external basal lamina and continuous to spindle nevus cells. Occasional NC cells contained a few melanosomes. There was no interposed axon in NC. Despite the close resemblance to Meissner corpuscle, NC showed no axonal supply. NC cells lacked terminal Schwannian differentiation and appeared to be modified melanocytes with some perineurial ultrastructural characteristics. The presence of CD34-positive cells, presumably corresponding to endoneurial fibroblasts, further supports an organizational relationship of NC and peripheral nerve sheath elements.

Pseudogranular Cell Tumor Of The Skin

A skin biopsy from a nasal lesion showed a dermal infiltrating neoplasm composed of polygonal cells with small nuclei and abundant coarsely granular eosinophilic cytoplasm. Light microscopic features were that of a granular cell tumor. However, the results of the immunohistologic studies and the observations of the electron microscopic studies did not identify the nature of the cells nor did they confirm that it was a granular cell tumor. We interpret the lesion as a pseudogranular cell tumor of the skin. SOURCE OF SUPPORT None REPORT OF A CASE A 66-year-old white female presented with a painless skin papule located on the right side of her nose that had been present for unknown period of time. There were no other symptoms and her past medical history was unremarkable. The biopsied skin lesion showed an intact normal epidermis. The dermis showed a proliferation of polygonal cells with abundant coarsely granular eosinophilic cytoplasm and small round or ovoid nuclei (Figs. 1 and 2) leading to an impression of a granular cell tumor. Figure 1 Figure 1: Dermal proliferation of polygonal cells with eosinophilic granular cytoplasm (low power). Figure 2 Figure 2: High power view of the tumor. Immunohistochemical stains showed that the tumor cells were positive for CD34, CD68, and vimentin and negative for S100 protein, Melan A, HMB45, Factor VIIIa, pancytokeratin, desmin, and SMA. Ultrastucturally (Fig. 3), the dermal polygonal cells showed numerous intracytoplasmic phagosome-like vesicles, many containing electron-dense irregular material. The mitochondria and endoplasmic reticulum were scarce. The cells did not show any features of melanocyte, Schwann cell or classic mitochondria-rich granular cells. Pseudogranular Cell Tumor Of The Skin 2 of 3 Figure 3 Figure 3: Electron microscopic picture showing numerous cytoplasmic phagosome-like vesicles. Mitochondria are scarce. No melanosomes or dense core granules are seen. 5000X. COMMENT Granular cell tumors are neural-derived tumors commonly arising in the upper aerodigestive tract and skin. A typical granular cell tumor of the skin is composed of polyhedral cells with large amount of granular eosinophilic cytoplasm involving the dermis. The cells are typically immunoreactive for S-100 protein signifying a neural origin and are negative for epithelial, muscle, and endothelial markers [1]. In our case, the polygonal dermal cells with eosinophilic granular cytoplasm, on immunostains, are not suggestive of a neural, melanocytic, epithelial, or smooth muscle origin. Electron microscopic observation of a lack of abundant lysosomes is unlike that of a granular cell tumor. Other primitive mesenchymal cell tumors may present as a granular cell proliferations. The CD34 and CD68 reactivity in our case may suggest that the polygonal cells are fibroblastic in origin. CD-34 positive and S-100 negative granular cell dendrocytosis has been described as a congenital lesion [2]). Another possibility considered was a possible oncocytic change in a dermal melanocytic nevus [3]. However, the cells in such cases are S-100 positive and ultrastucturally they show numerous mitochondria near the melanosomes. Other non-neural tumors showing nonspecific granular change include dermatofibroma, fibroxanthoma, leiomyoma, leiomyosarcoma, angiosarcoma, and basal cell carcinoma [4]. Our case did not show any microscopic, immunohistochemical, or ultrastuctural features of any of these tumors. The true origin of our tumor has not been established with certainty. Some of the nuclear changes observed in the ultrastrucural study may be indicative of apoptosis and the granular changes in the cytoplasm may represent degenerative changes. Pseudogranular cell tumor may be a reasonable descriptive name for such a lesion. CORRESPONDENCE TO Deba P Sarma, MD Department of Pathology Creighton University Medical Center Omaha, NE 68131 Tel: 402-449-4951 debasarma@creighton.edu

Collagenase-3 (MMP-13) Expression in Cutaneous Malignant Melanoma

Matrix metalloproteases (MMPs), enzymes with the ability to degrade the extracellular matrix, play an important role in tissue invasion by cutaneous malignant melanoma (CMM). One specific MMP, collagenase-3 (MMP-13), is thought to have a key function in the activation of MMP. To evaluate the expression of MMP-13 in CMM and assess its possible relationship to clinical and pathological parameters. MMP-13 expression was analyzed in 51 paraffin-embedded tumor samples from patients with invasive CMM, ten samples from in situ melanomas, and in eight samples from benign lesions (three dermal melanocytic nevi, three compound melanocytic nevi and two atypical melanocytic nevi) using immunohistochemical techniques. The median follow-up period in patients with invasive CMM was 50 months. Benign lesions were consistently negative for MMP-13, whereas three of the ten in situ melanomas (30%) and 23 of the 51 invasive CMMs (45%) showed positive immunostaining for MMP-13. The percentage of MMP-13-positive tumors correlated significantly and positively with the mitotic index (p=0.002) in invasive CMM. However, our results did not show any significant association between tumoral MMP-13 expression and relapse-free survival in patients with invasive CMM. MMP-13 appears to be a factor associated with tumor aggressiveness in CMM. It seems to eliminate an important barrier not only against tumoral invasion but also against proliferation.

Apolipoprotein D expression in cutaneous malignant melanoma.

Apolipoprotein D (Apo D) is a protein component of the human plasma lipid transport system, and an androgen-regulated protein in both breast and prostate cancer cell lines. Our goal was to evaluate the expression of Apo D in malignant cutaneous melanomas, as well as to assess its possible relationship to clinical and pathological parameters. Apo D expression was analyzed in 32 paraffin-embedded tissues from patients with invasive cutaneous malignant melanomas, in 8 samples from in situ melanoma, and in 10 samples from 10 benign lesions (4 dermal melanocytic nevi, 4 compound melanocytic nevi, and 2 dysplastic melanocytic nevi), using immunohistochemical techniques. The benign lesions were consistently negative for Apo D, whereas 3 of the 8 "in situ" melanomas (37.5%) and 12 of the 32 invasive melanomas (37.5%) showed positive immunostaining for Apo D. The percentage of Apo D-positive tumors was significantly higher in nodular than in superficial spreading melanomas (P = 0.011) and in melanomas with vertical growth phase than in melanomas with radial growth phase (P = 0.02). In addition, the percentage of Apo D-positive tumors was positively and significantly correlated with Clark's level of invasion (P = 0.046). Apo D may be a new prognostic factor of unfavorable evolution in cutaneous malignant melanoma.

Immunohistochemical Study of Pepsinogen C Expression in Cutaneous Malignant Melanoma: Association with Clinicopathological Parameters

The aim of this study was to evaluate the pepsinogen C expression in malignant cutaneous melanomas and analyze its possible relationship to clinical and pathological parameters. Pepsinogen C is an aspartyl proteinase primarily involved in the digestion of proteins in the stomach and represents one of the main androgen-inducible proteins in breast cancer cells. Tumoral pepsinogen C expression was retrospectively analyzed in 35 paraffin-embedded tissues from patients with primary malignant cutaneous melanoma and in 10 samples from 10 benign lesions (4 dermal melanocytic nevi, 4 compound melanocytic nevi and 2 dysplastic melanocytic nevi), using immunohistochemical methods. The benign lesions were consistently negative for pepsinogen C, whereas 20 of the 35 malignant melanomas (57%) showed positive immunostaining for pepsinogen C. The percentage of pepsinogen C-positive tumors was significantly higher in men than in women (p=0.01) and in epithelioid melanomas than in fusocellular or mixed type melanomas (p=0.003). In addition, the percentage of pepsinogen-C positive tumors was positively and significantly correlated with lesion thickness (p=0.003), Clark's level of invasion (p=0.028) and tumor stage (p<0.001). Pepsinogen C could be a new prognosticator of unfavorable outcome in cutaneous malignant melanoma.

Hobnail hemangioma ("targetoid hemosiderotic hemangioma"): clinicopathologic and immunohistochemical analysis of 62 cases.

Hobnail hemangioma, also known as "targetoid hemosiderotic hemangioma", represents a distinctive, benign vascular tumor, characterized histologically by a biphasic growth pattern of dilated vascular structures in the superficial dermis lined by prominent hobnail endothelial cells, and collagen dissecting, rather narrow neoplastic vessels in deeper parts of the lesion. We analyzed the clinicopathologic and immunohistochemical features in a series of 62 cases. Patient age range was 6-72 years (median: 32 years); 34 patients were male and 25 female. Clinically, a broad variation of diagnoses ranging from hemangioma to dermal melanocytic nevus and fibrous histiocytoma was suggested. Nineteen tumors arose in the lower and 13 in the upper extremities, 12 on the back, 8 in the buttock and hip region, and one case on the chest wall. Follow-up information on 35 patients (range from 1 to 4 years; mean: 1.5 years) revealed no local recurrence nor systemic metastasis. All neoplasms were located in the dermis and showed a broad morphologic spectrum in dependence of the age of the lesions. In addition to lesions resembling cavernous lymphangioma or lymphangioma circumscriptum, neoplasms were seen with morphologic features reminiscent to retiform hemangioendothelioma, progressive lymphangioma and so-called Dabska's tumor. Immunohistochemistry performed in 28 cases showed positive staining of tumor cells for CD31 in all cases tested, whereas only 3 out of 28 cases stained completely positive for CD34. In addition 4 out of 8 cases stained positively for vascular endothelial growth factor receptor-3 (VEGFR-3). Neoplastic endothelial cells were surrounded by actin-positive pericytes in only 7 out of 27 cases tested. Hobnail hemangioma occurs more frequently in male patients and arises commonly in the extremities and the trunk. Histologic and immunohistochemcial features suggest a lymphatic line of differentiation for this distinctive vascular neoplasm.

Widespread eruptive dermal and atypical melanocytic nevi in association with chronic myelocytic leukemia: case report and review of the literature

Eruptive nevi have been associated with local skin trauma and immunosuppression, and atypical eruptive nevi preceding melanoma have been reported in immunocompromised transplant patients. We describe a 25-year-old man with widespread eruptive atypical and dermal melanocytic nevi in association with chronic myelocytic leukemia. Our patient's disease differs from earlier reports of eruptive nevi because his nevi appeared before induction chemotherapy. Eruptive nevi may have been a prodrome to leukemia in this patient. His nevi were histologically similar to eruptive atypical nevi observed in AIDS patients and may imply a link between systemic immunosuppression and melanocyte proliferation. We suggest that patients in whom eruptive nevi develop in association with immunosuppression should be carefully observed for the development of melanoma skin cancer.

Solitary circumscribed neuroma of the skin (so‐called palisaded, encapsulated neuroma). Clinicopathological analysis of three cases with emphasis on differential diagnosis

AbstractThree cases of solitary circumscribed neuroma (so‐called palisaded, encapsulated neuroma) arising in the dermis have been studied. Two patients were male and one was female, with ages ranging from 27 to 59 years. All lesions arose on the forehead. Histologically, the neoplasms were partly encapsulated and were composed of broad fascicles, nests, and whorl‐like structures of bland appearing spindle cells often separated by artefactual clefts. Immunohistochemically. most of the tumour cells stained positive for S‐100 protein, and a considerable number also for CD 34, but failed to stain for epithelial membrane antigen and melanoma associated antigens. Solitary circumscribed neuroma has to be distinguished from long‐standing dermal melanocytic nevus, mucosal neuromas seen in type lib multiple endocrine neoplasia (MEN) syndrome, classical and cellular schwannoma, neurofibroma. perineurioma, traumatic neuroma, and angioleiomyoma.

Solitary circumscribed neuroma of the skin (so-called palisaded, encapsulated neuroma). Clinicopathological analysis of three cases with emphasis on differential diagnosis

Three cases of solitary circumscribed neuroma (so-called palisaded, encapsulated neuroma) arising in the dermis have been studied. Two patients were male and one was female, with ages ranging from 27 to 59 years. All lesions arose on the forehead. Histologically, the neoplasms were partly encapsulated and were composed of broad fascicles, nests, and whorl-like structures of bland appearing spindle cells often separated by artefactual clefts. Immunohistochemically, most of the tumour cells stained positive for S-100 protein, and a considerable number also for CD 34, but failed to stain for epithelial membrane antigen and melanoma associated antigens. Solitary circumscribed neuroma has to be distinguished from long-standing dermal melanocytic nevus, mucosal neuromas seen in type IIb multiple endocrine neoplasia (MEN) syndrome, classical and cellular schwannoma, neurofibroma, perineurioma, traumatic neuroma, and angioleiomyoma.

Melanocytic nevi in histologic association with primary cutaneous melanoma of superficial spreading and nodular types: effect of tumor thickness.

The histologic presence of benign dermal nevus cells in contiguity with primary cutaneous melanoma, as a distinct population separate from malignant melanocytes, was evaluated in a large referral data base. The melanomas were limited to superficial spreading melanoma (SSM) and nodular melanoma (NM). Overall, dermal melanocytic nevi were found associated with 1126 of 1954 primary SSM/NM (57.6%). When the melanomas were stratified by tumor thickness, an inverse relationship between the presence of benign nevus cells and tumor thickness was found: 64.9% of tumors less than 0.76 mm and 64.5% of those between 0.76 and 1.69 mm were associated with dermal nevi, whereas in the thickness range 1.70-3.60 mm, there were 45.6% associated nevi, and in melanomas greater than 3.60 mm, there were only 32.0% noted to have nevus cells. When melanomas were separated by nevus type, it was found that 41% were associated with an acquired pattern nevus, 38% with congenital pattern nevus, and 21% with dysplastic nevus. It may be concluded that 1) the histologic presence of nevus cells is a common event in SSM/NM; 2) the association of melanocytic nevus and melanoma is more easily demonstrated in thinner tumors; and 3) acquired pattern nevi, congenital pattern nevi, and dysplastic nevi are all potential precursors of melanoma.