Spitz nevus is a clinico-pathologic entity that can cause diagnostic concern, particularly in adults. Many studies have been performed to establish reliable histologic criteria, in the attempt to differentiate this lesion from melanoma. A series of 247 Spitz nevi, 6 of which were formerly classified as melanomas, were reviewed for clinical and histopathological parameters. Patients older than 20 comprised 66% of cases, with a predominance of women. The lower extremity was more affected in females of any age, whereas the trunk was more frequently involved in men over 40. Histopathologic examination showed the following differences among Spitz nevi related to age: acanthosis, parakeratosis, pagetoid infiltration, and Kamino bodies were more frequent in young people, whereas multinucleated melanocytes were more frequent in adults. The latter also had lesions that were less pigmented, with less maturation and more desmoplasia. At a mean follow-up of 94 months (range 52-172), recurrence at the site of biopsy or metastases were absent. In our study, a greater proportion of Spitz nevi occurred in adults than in previous series. Moreover, the relative incidence of Spitz nevus compared with melanoma in our population was higher than in other studies. Histopathologic criteria elaborated to diagnose Spitz nevus, applied to our cases, appeared reliable, allowing a correct diagnosis, even in adults.

Muir-Torre syndrome (MTS) is defined as the association of a sebaceous tumor or keratoacanthoma and an extracutaneous neoplasm, mainly from the gastrointestinal or genitourinary tracts. MTS is related to hereditary non-polyposis colorectal cancer (HNPCC), a syndrome with germline mutations in the mismatch repair (MMR) gene(s), leading to microsatellite instability (MSI). In this study, using immunohistochemistry and a microsatellite instability assay, we analyzed the incidence of MMR gene abnormalities in 79 sebaceous lesions from 70 patients, 26 of whom also had an extracutaneous visceral neoplasm. We were unable to investigate the family histories of our patients regarding other tumors in order to assess which of our cases met the Amsterdam criteria. Defective MMR protein expression (MMR-) was found in 18/70 (25.7%) patients, with an identical distribution between those having an isolated skin tumor (11/44, 25.0%) and those with an extracutaneous cancer (7/26, 25.4%). In the sporadic group, MMR negative lesions were significantly more frequent in extrafacial areas (P = 0.03). High concordance was found between MMR expression in sebaceous lesions and the extracutaneous neoplasm in the same patient (20/23, 86.9%), as well as between MMR expression and microsatellite status (18/20, 90%). In conclusion, this study confirms the value of immunohistochemistry to identify MMR defective tumors. However, since only a minority of sebaceous neoplasms in patients who also have an extracutaneous cancer display MMR defects, these techniques are of limited value for the identification of "clinically defined" MTS.

Multinucleate cell angiohistiocytoma (MCAH) is a putative reactive skin lesion, which has been reported mostly in adult female patients, and hormones have been recently suggested as a factor influencing its development. To test this hypothesis, monoclonal anti-estrogen receptor (ER) a, anti-progesterone receptor (PR), anti-Factor XIIIa, and polyclonal anti-vascular endothelial growth factor (VEGF) antibodies were applied by immunohistochemistry on a series of 21 MCAHs and, compared to 10 cases of dermatofibroma (DF) and 5 cases of chronic dermatitis presenting multinucleate cells. On normal skin surrounding the lesions and in cases of DF and chronic dermatitis, ERa was expressed in few undifferentiated and differentiated sebocytes, in few cells of anagen follicles and perifollicular mesenchymal cells, and in scattered dermal fibrocytes. In MCAHs, ERa was strongly expressed in interstitial spindle cells, spindle cells surrounding the characteristic vascular component of the lesion, and rare multinucleate cells. PR expression was restricted to sparse spindle cells and few sebocytes, whereas Factor XIIIa stained spindle cells in the dermis of normal and inflamed skin and in both MCAH and DF, and VEGF staining resulted completely negative. ERα, PR, and VEGF have been reported as poorly expressed in normal skin. In the present study, expression of ERα resulted upregulated in cases of MCAH, particularly in spindle cells, compared with that in DF cases. These findings underline the pathogenetic difference between MCAH and DF and also corroborate the suggested hypothesis of a role played by hormones, mainly ERα, in the development of this lesion. These observations could open a new strategy in the treatment of MCAH by antiestrogen therapy.

The pathogenesis of granuloma faciale (GF), framed in the group of cutaneous vasculopathic dermatitis, is poorly understood. The present study investigated whether GF might be part of the spectrum of IgG4-related sclerosing diseases (IgG4-RD). Erythema elevatum diutinum (EED), believed to belong to the same group of disorders as GF, was also studied for comparison. Thirty-one biopsies of GF obtained from 25 patients (18 men, 7 women) and 5 cases of EED (4 women and 1 man) were analyzed morphologically and for the expression of IgG and IgG4 by immunohistochemistry. The distribution of Th1, T regulatory and Th2 T-cell subsets, respectively, identified by anti-T-bet, anti-FoxP3, and anti-GATA-3 antibodies, was also evaluated. The dermal inflammatory infiltrate in GF contained eosinophils and plasma cells in variable proportions. Obliterative venulitis was found in 16 cases, and storiform fibrosis, a typical feature of IgG4-RD, was observed in 8 cases and was prominent in 3 of them. On immunohistochemical analysis 7 of 31 biopsies (22.6%) from 6 GF patients fulfilled the criteria for IgG4-RD (IgG4/IgG ratio >40%, and absolute number of IgG4 per high-power field >50). Interestingly, the 6 patients were male, and 4 showed recurrent and/or multiple lesions. In an additional 5 cases, only the IgG4/IgG ratio was abnormal. None of the 5 EED cases fulfilled the criteria for IgG4-RD. The T-cell subsets in GF were quite variable in number, GATA-3⁺ lymphocytes were generally more abundant, but no relationship with the number of IgG4⁺ plasma cells was found. The study indicates that a significant number of GF cases are associated with an abnormal content of IgG4⁺ plasma cells; this association was particularly obvious in male patients and in cases presenting with multiple or recurrent lesions. As morphologic changes typically found in IgG4-RD, such as obliterative vascular inflammation and storiform sclerosis, are found in GF, we suggest that GF might represent a localized form of IgG4-RD.

Annular lichenoid dermatitis of youth (ALDY) is a clinico-pathologic entity described in children and young patients, clinically reminiscent of morphea, annular erythema, vitiligo or mycosis fungoides. We report on six patients presenting single or multiple lesions, distributed particularly on the flanks and abdomen, with clinical and histologic features consistent with ALDY. Two patients were young girls and four were adults males. Three patients received topical therapy and four showed complete resolution of the lesions after a 24-65 months follow-up. Analogously to the cases reported so far, immunohistochemistry showed a T cell infiltrate with a predominance of CD8+ lymphocytes, while T cell receptor rearrangement was absent in all cases. It seems appropriate to include annular lichenoid dermatitis of youth among the dermatoses with a lichenoid pattern. For the first time, we found that it can affect also adult patients, therefore we propose to rename the disease annular lichenoid dermatitis. The differential diagnosis with mycosis fungoides, especially in adult patients, is particularly crucial for their proper management and treatment.