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A conjunctival Spitz nevus is a very rare, benign melanocytic lesion, which can be mistaken for a malignant melanoma. We present a case of a 28-year old man, who suffered from a rapidly growing, non-pigmented mass in the left caruncular area, extending to the nasal conjunctiva. The lesion was excised and pathologic examination showed nests of large, polygonal, non-pigmented epithelioid cells, located in the stroma. The overlying epithelium showed focal erosions. At the base, there was a lymphocytic infiltrate. Immunohistochemical techniques, with stainings for S-100 protein, HMB-45 and MIB-1, were used for further investigation and showed the melanocytic origin of the lesion (S-100 staining) as well as many cells in cell cycle (MIB-1 staining). However, no mitoses were seen. The clinical image, combined with pathologic and immunohistochemical findings, provided the diagnosis of a Spitz nevus localised in the conjunctiva. Although the cutaneous location of Spitz nevi is well known, conjunctival Spitz nevi are very rare and because of their mucosal origin, some of the histological features are different.
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PMID:A rare conjunctival Spitz nevus: a case report and literature review. 1789 90

Solitary primary melanocytic tumors of the central nervous system (CNS) represent a spectrum of lesions ranging from well-differentiated melanocytoma to melanoma. The association of a meningeal melanocytoma with an ipsilateral nevus of Ota is extremely rare, with only six cases reported in the literature to date. Only a minority of melanocytic tumors correspond to lesions of intermediate-grade malignancy, whose biological behavior and outcome remain undetermined. We report a new case of a 25-year-old man with a giant fronto-temporal intracranial meningeal melanocytoma associated with a congenital nevus of Ota, who suffered an acute neurological deterioration requiring an emergent surgical procedure. Despite total removal of the lesion, the patient did not recover from the operation due to a malignant infarct of the right hemisphere. The lesion showed no histological criteria of malignancy but did exhibit an elevated (8%) MIB-1/Ki-67 cell proliferative index, which suggested an intermediate-grade melanocytoma. In addition, its metabolic profile, determined by in vivo proton magnetic resonance spectroscopy (MRS), was similar to that observed in most high-grade gliomas. To our knowledge, this is the first case of a meningeal melanocytoma of intermediate grade associated with a nevus of Ota reported in the literature. Only two additional intermediate-grade melanocytomas showing an elevated MIB-1/Ki-67 labeling index have been previously reported. The MIB-1/Ki-67 labeling index may have potential prognostic value in helping the clinician to predict an aggressive clinical behavior and/or malignant progression for primary melanocytic neoplasms of the CNS.
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PMID:Intracranial intermediate-grade meningeal melanocytoma with increased cellular proliferative index: an illustrative case associated with a nevus of Ota. 1944 82

Ancient melanocytic nevus (AN) is an unusual but distinctive melanocytic neoplasm within the spectrum of simulators of malignant melanoma. This report describes 13 patients with AN where a long follow-up information was available. Histopathology is characterized by 2 populations of melanocytes, namely, one with large pleomorphic cells and the other with small melanocytes. A few mitotic figures may be present exceptionally. MIB-1 (Ki67) proliferation marker reveals an overall low nuclear labeling index. Additional important findings are stromal degenerative changes. AN must be especially differentiated from dermal melanoma arising in a nevus.
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PMID:Ancient melanocytic nevus: a simulator of malignant melanoma. 2139 48

Blue nevi are a clinically and pathologically heterogeneous group of benign pigmented dermal melanocytic tumors that may exhibit histologic overlap with malignant melanoma. This study evaluates the role of immunohistochemical and molecular analyses in the classification and differential diagnosis between blue nevi and melanoma. Twenty-three dermal melanocytic tumors, initially diagnosed as benign or ambiguous, were subjected to immunohistochemical staining for phosphohistone H3 and MIB-1 to evaluate mitotic activity, comparative genomic hybridization to detect chromosomal aberrations, and GNAQ, GNA11, BRAF, NRAS, and KRAS sequencing. Of 19 patients with follow-up information (median, 1.6 years), 3 developed recurrent or metastatic disease. Nevertheless, 11 of the 19 patients with follow-up had <2 years of follow-up. Nine of 23 patients showed chromosomal aberrations, including all 3 patients with tumor recurrence or progression. There was no significant correlation between mutation status (P = 0.6) or mitotic rate (P = 0.3) and outcome. In conclusion, three of nine patients with chromosomal aberrations developed tumor recurrence or progression. Patients with histologically ambiguous dermal melanocytic proliferations that exhibit copy number aberrations should undergo careful clinical follow-up.
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PMID:Proliferative activity, chromosomal aberrations, and tumor-specific mutations in the differential diagnosis between blue nevi and melanoma. 2326 Dec 61

Spitz nevi account for approximately 1% of all melanocytic nevi of the skin in children. Although Spitz nevi often develop in the skin of the head and neck, intraoral Spitz nevi are rare. These nevi contain epithelioid and spindle cells and exhibit cytologic and architectural atypia when compared with routine melanocytic nevi, and may be mistaken for atypical Spitz tumor, Spitzoid melanoma, or conventional melanoma. Here, we report a Spitz nevus on the buccal mucosa of an 11-year-old boy. The tumor was composed of a proliferation of mostly epithelioid melanocytes with a smaller spindle cell component. The melanocytes were positive for S100, MART-1, and p16 proteins, with HMB-45-positive cells located only in the basal cell layer and superficial lamina propria. Less than 5% of the nuclei were positive for MIB-1, and there were no mitotic figures. We review the literature on 7 previously reported cases of Spitz nevi.
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PMID:Intraoral Spitz nevus: case report and literature review. 2413 94

Neurocutaneous melanosis (NCM) is a rare congenital disorder characterized by the association of large and/or multiple congenital melanocytic nevi (CMN) of the skin with melanocytic lesions of the leptomeninges, including melanocytosis. Leptomeningeal melanocytosis carries a poor prognosis once neurological symptoms develop. Despite surgery, which is often not radical, few other treatment options exist. Recently, it was demonstrated that early embryonic, post-zygotic somatic mutations in the NRAS gene are implicated in the pathogenesis of NCM.In this report, we present a 13-year-old boy with NCM and progressive symptomatic leptomeningeal melanocytosis. A somatic NRASQ61K mutation was present in both CMN as well as the melanocytosis. Despite repeated surgery, the patient showed clinical progression. Therefore, treatment with MEK162, a MEK inhibitor, was started on compassionate use base. The patient died only five days later, i.e. too early to expect a clinical effect of MEK162 therapy. We therefore studied the effect of MEK162 at the protein level in the leptomeningeal tumor by immunohistochemical and Western Blot analyses using Ki67 and pERK antibodies. We observed lower MIB-1 expression and lower pERK expression in the post-treatment samples compared to pre-treatment, suggesting a potential effect of MEK inhibiting therapy. Further studies are needed to determine whether MEK inhibitors can effectively target NRAS-mutated symptomatic NCM, a rare but potentially fatal disease.
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PMID:Experimental treatment of NRAS-mutated neurocutaneous melanocytosis with MEK162, a MEK-inhibitor. 2471 50

Dear Editor, I read an interesting recent article by Karimzadeh et al. (1) in an earlier issue of your journal, who provided a comprehensive review addressing a relatively rare benign tumor originating from the hair follicles - trichoepithelioma (TE). They rightly claimed that trichoepithelioma can be divided into the following 3 subgroups: a) multiple familiar TE, b) solitary non-hereditary TE, and c) desmoplastic trichoepithelioma (DTE). I would like to stress that the last category represents a distinct variant with some unique clinical and particularly histopathological characteristics. However, Karimzadeh et al. (1) did not provide any further information on DTE in their review. In my opinion, this variant of TE deserves special mention. The main reason is that it histomorphologically mimics infiltrative (morpheic) basal cell carcinoma (BCC) and can be challenging to differentiate for pathologists, particularly in small biopsies (2-5). Therefore, I report the case of young woman with two simultaneously growing DTEs with emphasis on the histopathology of this tumor. A 32-year old woman presented with two skin lesions arising on the left side of the forehead and on the right side of the neck. She claimed they had been present for one year. On gross examination, the lesion arising on the forehead was flat, whitish, and about 10 mm in diameter. The lesion on the neck was flat, light brownish, and 6 mm in diameter. A total surgical extirpation was performed. At a low magnification, both lesions histologically mimicked infiltrative (morpheic) BCC of the skin. However, more detailed inspection of individual microscopic features excluded this diagnosis. The tumors were composed of narrow lines and irregular strands of basaloid epithelial cells embedded in a dense stroma (Figure 1). Neoplastic aggregates grew within the dermis and were not attached to the surface epidermis. In the larger lesion, they extended into the subcutaneous fat. No ulceration was present. At high magnification, the tumor cells presented a bland appearance with prominent oval nuclei and scant cytoplasm (Figure 2). There were some signs that abortive follicular (hair bulb) differentiation occurred. Nuclear pleomorphism and mitotic figures as well as peripheral palisading and tumor-stroma retraction phenomenon were not present. Furthermore, sporadic keratinous cysts lined by stratified squamous epithelium were found. The stroma was densely collagenous, hypocellular, without solar elastosis, and without any inflammatory infiltration. Foreign body type granulomas with multinucleated giant cells were sometimes present, usually in relation to disrupted keratinous cysts. Calcifications were observed in both lesions, and ossification also occurred in the larger tumor. Immunohistochemically, the tumor was positive for high molecular weight cytokeratin (clone 34bE12) and epithelial antigen (clone BerEP4) (Figure 3). A few cells immunoreactive for cytokeratin 20 (CK20, clone Ks20.8) were observed within tumor aggregates. The Ki-67 proliferation index (clone MIB-1) did not exceed 10%. A spectrum of histomorphological findings of both lesions were consistent with DTE. Resection margins were intact and no local recurrence has been observed at the time of this writing. The differential diagnosis between DTE and infiltrative BCC is sometimes exceedingly difficult, even when assessed by a dermatopathology expert. However, establishing the correct diagnosis is crucial for clinicians, as the first entity represents a benign adnexal tumor with an excellent prognosis, while the latter is a high-risk variant of BCC that requires much more stringent clinical management. As we have already pointed out, both tumors share many histomorphological features. Firstly, they both consist of small strands and thin cords of basaloid epithelial cells in a densely sclerotic stroma. Several attempts have been made to provide reliable and reproducible criteria for their differentiation. An excellent description of various histopathological features that help to discriminate DTE from infiltrative BCC has been published by Costache et al. (3). They studied samples from 19 DTEs and 18 infiltrative BCCs. They revealed that the most reliable findings that favored a diagnosis of DTE rather than infiltrative BCC were as follows: architectural symmetry and well-circumscribed lesions, depression in the center of the tumor, connection of tumor aggregation to infundibula, at least one sign of follicular, infundibular, or sebaceous differentiation, granulomatous giant cell reaction due to rupture of keratinous cysts, foci of calcification and ossification, no tumor-stroma clefting, absence of solar elastosis, and association with melanocytic nevus. Another set of criteria also thought to provide significant diagnostic evidence for DTE was the lack of connection of neoplastic nests to the surface epidermis, the clefts between the peritumorous stroma and the surrounding dermis, and the presence of cut artefacts (knife marks) in histologic sections. In challenging cases, immunohistochemical stains for CK20 and androgen receptors can be helpful in discriminating between DTE and BCC. While TEs usually contain at least a few CK20-positive Merkel cells and are negative for androgen receptors, BCCs are mostly negative for Merkel cells and positive for androgen receptors (2,3). However, the diagnostic limitation of these markers should be kept in mind. For example, an expression of androgen receptors is often focal and sometimes completely absent in BCCs (2). On the other hand, many TEs have very low density of colonizing Merkel cells, which may require serial sections for reliable detection (2). Along with histopathology, clinical aspects have also to be taken into consideration when deciding on the final diagnosis. DTE occurs mainly in young and middle-aged women and has a predilection for the face, principally for the cheeks (4,5). In contrast, an age of the onset is much higher and a prevalence of women much lower in cutaneous BCCs (6). Overall, DTE is an uncommon adnexal tumor and its aggressive histological features can cause diagnostic uncertainty and confusion with infiltrative BCC. Distinguishing of these two structurally similar but biologically completely different tumor entities often requires a comprehensive diagnostic approach that includes the complexity of histopathological, immunohistochemical, and clinical findings.
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PMID:Desmoplastic Trichoepithelioma: An Uncommon but Diagnostically Problematic Benign Adnexal Tumor. 3196 46


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