A murine model for the development of melanocytic nevi and their progression to melanoma.

Acquired melanocytic nevi are commonly found in sun exposed and unexposed human skin, but the potential for their transformation into invasive melanoma is not clear. Therefore, a mouse model of nevus initiation and progression was developed in C3H/HeN mice using a modified chemical carcinogenesis protocol. Nevi develop due to DNA damage initiated by dimethylbenz(a) anthracene (DMBA) followed by chronic promotion with 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Dysplastic pigmented skin lesions appeared in 7-9 wk with 100% penetrance. Nests of melanocytic cells appeared in a subset of skin draining lymph nodes (dLN) by 25 wk, but not in age matched controls. Immunohistochemistry, real-time PCR, and flow cytometric analyses confirmed their melanocytic origin. Transformed cells were present in a subset of nevi and dLNs, which exhibited anchorage-independent growth, tumor development, and metastasis in nude mice. Approximately 50% of the cell lines contained H-Ras mutations and lost tumor suppressor p16(Ink4a) expression. While most studies of melanoma focus on tumor progression in transgenic mouse models where the mutations are present from birth, our model permits investigation of acquired mutations at the earliest stages of nevus initiation and promotion of nevus cell transformation. This robust nevus/melanoma model may prove useful for identifying genetic loci associated with nevus formation, novel oncogenic pathways, tumor targets for immune-prevention, screening therapeutics, and elucidating mechanisms of immune surveillance and immune evasion.

A Histological Snapshot of Hypothetical Multistep Progression From Nevus Sebaceus to Invasive Syringocystadenocarcinoma Papilliferum.

Syringocystadenocarcinoma papilliferum (SCACP) is an extremely rare adnexal neoplasm, believed to arise in a preexisting nevus sebaceus of Jadassohn (NSJ) through a multistep progression process. This hypothetical process involves an NSJ giving rise to syringocystadenoma papilliferum, which then presumably undergoes malignant transformation in rare circumstances to give rise to SCACP in situ, which finally progresses to an invasive SCACP. Of the 30 SCACP cases reported so far, none have documented the process from a birthmark to the final invasive lesion, with histological evidence of each step, in a single tumor. Here, the authors report just such a case. A 74-year-old man presented with a recently enlarging birthmark on the scalp. Excisional biopsy showed an invasive SCACP, in the background of SCACP in situ, syringocystadenoma papilliferum, and NSJ. Furthermore, this tumor showed a concurrent pigmented trichoblastoma and histological evidence of lymphovascular invasion, events that have not been documented with SCACP. Interestingly, all these component lesions were present on a single histological section of this solitary tumor. Regional lymph node metastasis, a rare occurrence in SCACP, was also present in this remarkable case. The authors discuss the implications of these findings in light of the review of relevant literature.

Dermatological clues to the diagnosis of atypical complete DiGeorge syndrome.

Atypical complete DiGeorge syndrome (DGS) is an extremely rare congenital disease characterized by an eczematous dermatitis, lymphadenopathy, and an oligoclonal T-cell proliferation. Because its initial presentation may be confused with other types of eczematous dermatitis, diagnosis and treatment are usually delayed. We describe herein a case of an infant with atypical complete DGS to draw attention to the clinical and histopathological findings that lead us to the diagnosis.

Chondroid melanoma metastatic to lung and skin showing SOX-9 expression: a potential diagnostic pitfall.

Melanoma is a malignant neoplasm that shows multiple morphological appearances resembling other tumors and therefore may generate diagnostic pitfalls. In cases of metastatic melanoma, when the primary skin lesion has gone undiscovered or has not been brought to the attention of the clinician or pathologist, the metastatic lesion can be misdiagnosed as sarcoma, carcinoma, or lymphoma. Melanomas with differentiation toward mesenchymal elements are particularly perilous in this regard. Here, the authors report a case of metastatic melanoma that was misdiagnosed as extraskeletal myxoid chondrosarcoma. This case highlights the potential diagnostic pitfall posed by metastatic melanoma with chondroid matrix and SOX-9 expression.