'Tubular' structures within melanocytic proliferations: a distinctive morphologic finding not restricted to Spitz nevi

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.

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.

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.

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.