'Tubular' epithelioid cell nevus: a new variant of Spitz's nevus

The Spectrum of Spitz Melanocytic Lesions: From Morphologic Diagnosis to Molecular Classification

Spitz tumors represent a distinct subtype of melanocytic lesions with characteristic histopathologic features, some of which are overlapping with melanoma. More common in the pediatric and younger population, they can be clinically suspected by recognizing specific patterns on dermatoscopic examination, and several subtypes have been described. We now classify these lesions into benign Spitz nevi, intermediate lesions identified as “atypical Spitz tumors” (or Spitz melanocytoma) and malignant Spitz melanoma. More recently a large body of work has uncovered the molecular underpinning of Spitz tumors, including mutations in the HRAS gene and several gene fusions involving several protein kinases. Here we present an overarching view of our current knowledge and understanding of Spitz tumors, detailing clinical, histopathological and molecular features characteristic of these lesions.

A Case of Compound Nevus with Intradermal Pseudoglandular Features: A Rare Variant and Possible Pitfall

Melanocytic nevi are frequent cutaneous lesions with a large variation of morphological features, including pseudoglandular formation, which has rarely been described in the literature and remains of uncertain biological and clinical significance. We report a case of benign compound melanocytic nevus, with a dermal component showing an epithelioid proliferation arranged in small nests with central lumen-like structures mimicking glands. Immunohistochemical staining was necessary to determine the exact nature of the proliferation, since the tubular differentiation can be seen in benign and malignant epithelial neoplasms and has to be clearly identified to avoid misdiagnosis.

Two cases of discrete adenoid pseudogland formation within benign intradermal melanocytic nevi

We report 2 cases of benign intradermal melanocytic nevi with discrete glandular elements and mucin deposition engendering a diagnostic dilemma. The preliminary differential included entrapment of adnexal structures, collision with an adnexal neoplasm such as adenoid cystic carcinoma or metastatic adenocarcinoma. A colloidal iron special stain confirmed the deposition of mucin; however, a pankeratin AE1/AE3 immunohistochemical cocktail was surprisingly negative. Closer cytological examination of the discrete "glands" combined with nearby pseudoangiomatous (almost kaposiform) change hinted at melanocytic origin, which was confirmed with a positive melanoma antigen recognized by T-cells 1 immunohistochemical stain. Histopathological variations in melanocytic morphology include balloon cell formation, pseudoangiomatous change, lipomatous change, nevus of Nanta (osteonevus) with osseous metaplasia, neurotization, cartilaginous nevus, calcification, increased elastic tissue, psamomma body formation, amyloid deposition, eczematous changes (Meyerson nevus), granular cell change and ancient change/atypia. Mucin deposition, tubule and pseudoacini formation, and now discrete adenoid cystic-like "glands" may also be seen, all of which are important to recognize to avoid misdiagnosis.

Spitz Tumors of the Skin

Spitz tumors are melanocytic neoplasms hallmarked by large cell size, lack of high-grade atypia, and a regular architecture. Most are nonpigmented or poorly pigmented. Malignant potential ranges from absent (Spitz nevus), to fully present (spitzoid melanoma), with a further, ill-defined group of Spitz tumors with limited metastatic potential. Microscopic evaluation may prove inconclusive in some instances, resulting in a verdict of Spitz tumor of uncertain malignant potential (STUMP). STUMP is, therefore, not an entity, and should not be equated with Spitz tumors with limited metastatic potential. Novel diagnostic techniques are yielding promising results, and further evaluation is ongoing.

Unusual Histopathological Patterns in Melanocytic Nevi With Some Previously Undescribed Patterns

Melanocytic nevi are one of the most common diagnoses in the daily practice of any dermatopathologist. Although in the vast majority of cases the final diagnosis is not difficult, there are certain rare and unusual morphologic variations that can elicit some diagnostic problems. Although some of these variations can be considered as mere morphologic oddities, others might lead to a differential diagnosis with melanoma, or with other tumors, including epithelial or neural tumors. In the current report, we review many of these morphologic variations and discuss the main differential diagnosis, when appropriate.

Epithelioid melanocytic nevus with tubule and pseudoacini formation

A 26-year-old female presented with a 7 mm irritated pink-red papule on the left posterior shoulder. A shave biopsy revealed a dermal proliferation of epithelioid cells arranged in small nests with central lumen-like structures resembling glands set in a densely sclerotic stroma. S100 and Melanoma antigen recognized by T cells 1 (MART-1) immunohistochemical positivity confirmed a dermal melanocytic neoplasm. Pan-cytokeratin and cytokeratin 7 were negative within the nests ruling out an adnexal neoplasm or metastatic adenocarcinoma. A Spitz nevus variant characterized by the presence of focal tubular structures (tubular epithelioid cell nevus) has rarely been described in the literature and is of uncertain biological significance. Similar structures have also been observed in Clark/dysplastic nevi and melanoma. Glandular differentiation is seen in a wide variety of benign and malignant epithelial neoplasms; however, melanocytes are not known to be capable of forming true glands. The exact mechanism and significance of this phenomenon are currently unknown. Certain postulations include central melanocyte apoptosis, autocrine or paracrine factor secretion or retraction artifact caused by tissue fixation. This distinctive finding is important to recognize in order to avoid misdiagnosis as a glandular neoplasm.

Rosette-like structures in the spectrum of spitzoid tumors

BACKGROUND

Spitz nevi demonstrate a diverse spectrum of morphologies. Recently, there have been two reported examples of Spitz nevi with rosette-like structures similar to Homer-Wright rosettes. Rosettes have also been described in melanomas and in a proliferative nodule arising in a congenital nevus.

METHODS

A retrospective review of 104 cases of Spitz nevi and variants (n = 51), pigmented spindle cell nevi (n = 26), combined melanocytic nevi with features of Spitz (n = 8), atypical Spitz tumor (AST, n = 9), and spitzoid melanoma (n = 10).

RESULTS

Rosette-like structures were present in 3 of the 104 cases (2.9%), including a compound Spitz nevus, a desmoplastic Spitz nevus, and an AST. All three cases demonstrated several foci of small nests of epithelioid cells with peripherally palisaded nuclei arranged around a central area of fibrillar eosinophilic cytoplasm. Immunohistochemical staining of the three spitzoid lesions demonstrated that the rosette-like structures express S100 protein, Melan-A, and neuron specific enolase (NSE) and lacked expression of neurofilament, glial fibrillary acidic protein and synaptophysin.

CONCLUSIONS

While uncommon, rosette-like structures can occur as a focal feature in Spitz nevi and AST. Rosette-like structures may represent a normal morphologic finding in Spitz nevi, and awareness of them may prevent misdiagnosis as a neural tumor or melanoma.

A curious serendipitous finding: Spitz naevus combined with a syringoma

Combined tumours are often a serendipitous finding. Among the spectrum of melanocytic tumours, the co-existence of different cell populations of the same lineage is a well-recognised phenomenon. Less commonly documented, but still well documented is the event of a melanocytic tumour in collision with an epithelial benign or malignant neoplasm. Exceptionally infrequent is however the collision of a Spitz naevus with an epithelial tumour. Here we report the clinical-dermoscopic and histopathological findings of a Spitz naevus occurring in collision with a syringoma.

Spitz nevus: a clinicopathological study of 349 cases

Spitz nevus is an infrequent, usually acquired melanocytic nevus composed of epithelioid and/or spindle melanocytes that can occasionally be confused with melanoma. Currently, there are no immunohistochemical markers or molecular biology techniques that can be used to make an entirely safe diagnosis of Spitz nevus or melanoma in problematic cases. A retrospective study has been carried out that included all the cases diagnosed as Spitz nevus from our files. Follow-up information of the patients was unavailable. Three hundred forty-nine cases of unequivocal Spitz nevi were included, and their clinical and histopathological parameters were reviewed. One hundred and forty patients (40%) were 15 years old or younger, with a male to female ratio of 1:1. In patients older than 15 years, there was an evident predominance of women, with a male to female ratio of around 1:3. Spitz nevus was most commonly located on the lower extremities, followed by the trunk in both children and adults. Despite the fact that the head and neck were the third most common location in children, it was a much more frequent location in children than in adults. The constitution by epithelioid and/or spindled cells was the only histopathological finding present in 100% of cases. The other pathological findings studied were, from more to less frequent: maturation (72%), inflammatory infiltrate (70%), epidermal hyperplasia (66%), melanin (50%), telangiectasias (40%), Kamino bodies (34%), desmoplastic stroma (26%), mitosis (23%), pagetoid extension (13%), and hyalinization of the stroma (8%). Hyalinization was the only histopathological parameter that was statistically more frequent in adults than in children.

Unusual occurrence of a melanoma with intermixed epithelial component: a true melanocarcinoma?: case report and review of epithelial differentiation in melanoma by light microscopy and immunohistochemistry

We report a case of a 27-year-old woman with a nonpigmented lesion on the right scalp. Histological examination showed a malignant nodular neoplasm with 2 distinct but intimately admixed components: a malignant melanoma with a spindle component and an unusual glandular component. Immunohistochemical studies demonstrated epithelial differentiation on the basis of cytokeratin (CAM5.2 and AE1/AE3) expression in the glandular component and melanocytic differentiation (HMB-45, PNL2, MITF, and S-100) of the spindle cell component. A single melanocytic marker (MITF) was expressed in both components, raising the possibility of dual differentiation in a single tumor, rather than the alternative considerations of a collision tumor or a reactive pseudoepitheliomatous hyperplasia with eccrine duct lumen formation within a melanoma. This unusual tumor with both melanocytic and epithelial components may represent a true melanocarcinoma, which becomes a plausible consideration, in view of melanoma plasticity and recent experimental evidence and speculation about the role of stem cells in melanoma.

Hyalinizing Spitz Nevus: Spindle and Epithelioid Cell Nevus with Paucicellular Collagenous Stroma

Hyalinizing spindle and epithelioid cell nevus (Spitz nevus) is an uncommon melanocytic lesion. The histologic features of this benign tumor can mimic those of certain benign (dermatofibroma and desmoplastic cellular blue nevus) and malignant (metastatic carcinoma and malignant melanoma) neoplasms. We report a woman with a hyalinizing Spitz nevus and review the clinical characteristics, histologic features, and differential diagnosis of this lesion. The lesion presented as an asymptomatic red firm nodule on her abdomen. Microscopic examination showed a symmetric lesion in the dermis. The neoplastic cells were large and epithelioid-shaped or plump and spindle-shaped. They were present as isolated individual cells, single cells in a linear pattern, small nests, and fascicles in a paucicellular hyalinized stroma. Neoplastic cells with prominent eosinophilic nucleoli were evenly exhibited from the superficial to deep lesion. Diffuse expression of S-100 protein and absence of staining with antibodies to cytokeratin and HMB-45 were observed. The features were diagnostic of a hyalinizing Spitz nevus. Hyalinizing Spitz nevus is a benign lesion whose histologic features may mimic dermatofibroma, desmoplastic cellular blue nevus, metastatic carcinoma, and malignant melanoma. Immunohistochemical studies are helpful to differentiate these lesions.

Spitz nevus and its histologic simulators

Spitz nevi continue to pose a considerable diagnostic challenge to the histopathologist. Key features of Spitz nevus and its variants are discussed and contrasted with the telltale signs of malignancy of "Spitzoid" melanomas. The importance of the histologic features of the deep, rather than superficial, part of the lesions is emphasized.

Plexiform spitz nevus

In 1999, Spatz et al. reported the first 2 cases of a plexiform variant Spitz nevus. We describe another case of this variant on the upper thigh of a 10-year-old boy and discuss the differential diagnosis. Histologically, it comprised nodules of epithelioid cells with a plexiform arrangement distributed throughout the superficial and deep dermis. The cells had moderate eosinophilic cytoplasm with vesicular nuclei and prominent nucleoli. Intranuclear inclusions were present focally. The tumor nodules were embedded in a myxoid stroma with intratumoral and peritumoral inflammatory cells including both lymphocytes and eosinophils. There were occasional melanin-containing spindle-shaped cells. An intraepidermal component could not be assessed, since the lesion was ulcerated. The differential diagnosis includes both melanocytic and nonmelanocytic lesions exhibiting a plexiform pattern of growth as well as myxoid lesions.

Angiomatoid Spitz nevus: a distinct variant of desmoplastic Spitz nevus with prominent vasculature

Five cases of a distinctive variant of desmoplastic Spitz nevus are reported. To the best of our knowledge, this tumor has never been described previously. Clinically, it presents itself as a solitary papule on the extremities of young adults. Microscopically, it shows predominance of solitary melanocytes with epithelioid appearance over cell nests. They are embedded in a prominent fibrous stroma with many densely arranged, small blood vessels with plump endothelia not seen in other Spitz nevi. Because of its resemblance to a vascular tumor, the name angiomatoid Spitz nevus is proposed for this lesion. Absence of recurrences or metastases after complete excision in all cases supports the benign nature of the tumor.