Vascular neoplasm or pseudovascular nevus? Potential pitfalls in diagnosis.

Melanocytic nevi, on histopathologic evaluation, occasionally contain slit-like clefts or spaces that may resemble vascular or lymphatic spaces. The spaces may contain blood or, perhaps more concerning, nests of melanocytes that could suggest lymphatic invasion of melanoma. When lined by melanocytes rather than true endothelium, these pseudovascular spaces within melanocytic nevi are generally attributable to tissue processing artifact. When the space in question is pronounced, a proper diagnostic work-up is prudent in order to exclude a true vascular neoplasm or melanoma. In this case series we present several melanocytic lesions with prominent vascular-appearing spaces that warranted further investigation.

Animal-type melanoma: a clinical and histopathological study of 22 cases from a single institution.

Background Animal-type melanoma is a rare distinct melanoma subtype, characterized by proliferation of heavily pigmented epithelioid and spindled melanocytes that resembles the heavily pigmented melanomas seen in grey horses. While animal-type melanoma is generally considered to be more indolent than conventional melanoma, only a limited number of cases have been reported and, as such, the clinical characteristics of animal-type melanoma are incompletely understood. Objectives To characterize the clinical and histopathological features of animal-type melanoma, and determine any features that may predict outcome. Patients/Methods Data was extracted from a prospectively collected melanoma database (1994-2008), and a retrospective pathology database (1991-2008) for all patients with a diagnosis of both equivocal (8) and unequivocal (14) malignant animal-type melanoma. We reviewed the clinical and histopathological features, including the sentinel lymph node biopsy (SLNB) status. Results A total of 22 patients were identified, with a median age of 35 years. The median Breslow depth was 2.22 mm. A SLNB was performed in 17 patients, eight (47%) were positive. Younger age was associated with: (i) animal-type melanoma with features equivocal for malignancy (median age of 7 vs. 48 years, P = 0.01), and (ii) a negative SLNB (median age 12 vs. 53 years, P = 0.03). Four patients with unequivocal animal-type melanoma developed recurrent metastatic disease, with one patient death. No patient with an equivocal animal-type melanoma or negative SLNB developed recurrent disease; however, this did not reach statistical significance (P = 0.13 and P = 0.09, respectively). Conclusions Animal-type melanoma has a propensity for regional lymphatic metastasis and is rarely capable of disseminated metastatic disease and death. Animal-type melanoma appears to exhibit a spectrum of biological behaviour, with young patient age associated with more indolent disease.

White sponge nevus presenting as genital lesions in a 28-year-old female.

A case is presented of white plaques occurring predominantly on the vulvar mucosa of a 28-year-old female diagnosed as white sponge nevus (WSN). WSN is a rare, autosomal dominant disorder involving mucous membranes. It predominantly affects the oral mucosa; however, it has been reported to rarely involve extraoral mucosal sites. In this case, histology and family history were key features leading to the correct diagnosis. WSN is an extremely rare cause of vulvar leukoplakia, yet it is important to recognize to allow for appropriate genetic counseling of this autosomal dominant disorder and to avoid misdiagnosis and the potential for subsequent exposure to ineffective treatment modalities.

S100A6 preferentially labels type C nevus cells and nevic corpuscles: additional support for Schwannian differentiation of intradermal nevi.

BACKGROUND: Melanocytic nevi typically show a morphologic sequence of maturation from epithelioid "type A" cells to fusiform, Schwann cell-like "type C" cells with dermal descent. Nevi may also produce Wagner-Meissner-like structures (nevic corpuscles). Previous studies have shown that this maturation of intradermal nevi recapitulates intermediate stages in Schwann cell development. In intradermal nevi, we have evaluated the pattern of S100A6 protein, a form of S100 found in Schwann cells. METHODS: Formalin-fixed, paraffin-embedded archival tissues were evaluated by immunohistochemistry using antibodies specific for S100A6 and S100B in 38 intradermal nevi (IDN). Ten neurofibromas (NF), 3 Schwannomas (SCH), 2 palisaded and encapsulated neuromas (PEN), and 2 granular cell tumors (GCT) were included as positive controls since these lesions have large numbers of Schwann cells. RESULTS: Melanocytic nevi demonstrated preferential anti-S100A6 staining of "type C" cells (36/38; 28 strong, 8 weak) and nevic corpuscles (25/38; 19 strong, 6 weak) compared to "type A" cells (17/38; 17 weak) and "type B" cells (17/38; 4 strong, 13 weak). All NF, SCH, and PEN stained strongly with anti-S100A6. Both GCT were negative with anti-S100A6 but positive with anti-S100B. CONCLUSIONS: The pattern of S100A6 expression in intradermal nevi further supports the hypothesis that maturation in these lesions recapitulates features of Schwann cell differentiation. The lack of S100A6 expression by both GCT suggests that these lesions have lost this feature of Schwann cells, which may play a role in their peculiar phenotypic appearance.

S100A6 expression in fibrohistiocytic lesions.

BACKGROUND: S100A6, an S100 calcium-binding protein, has been found in a variety of cutaneous and extracutaneous lesions including: melanocytic nevi, melanoma, some salivary gland and epithelial tumors, and malignant fibrous histiocytoma (MFH). Dermal dendrocytes (DD) in the papillary dermis of skin also express S100A6 protein. We evaluated a variety of cutaneous fibrohistiocytic lesions to determine if the immunophenotype of S100A6 positivity can be expanded to include some or all of these lesions. METHODS: Formalin-fixed, paraffin-embedded tissues from fibrous papules (FP, 20), dermatofibromas (DF, 20), dermatofibrosarcoma protuberans (DFSP, 5), atypical fibroxanthomas (AFX, 5), oral fibromas (3), digital fibroma (1), and dermatomyofibroma (1) were evaluated with antibodies to S100A6, S100B, factor XIIIa, and MAC387 using a one-hour capillary action-based immunohistochemical procedure. RESULTS: DD in 20/20 FP, 19/20 DF, and 4/4 fibromas stained positively with anti-S100A6 in a pattern similar to anti-factor XIIIa. No DFSP cases stained with anti-S100A6. Anti-S100A6 showed superior staining to anti-factor XIIIa in 4/5 AFX cases. CONCLUSIONS: The immunophenotypes of some fibrohistiocytic lesions can be expanded to include S100A6 protein. With the exception of AFX, the use of anti-S100A6 does not appear to offer added benefit over anti-factor XIIIa in the differential diagnosis of fibrohistiocytic lesions.

Revisiting the issue: can the reading for serologic reactivity following 37 degrees C incubation be omitted?

BACKGROUND: Omitting the 37 degrees C reading from screening tests for unexpected antibodies results in failure to detect some Rh, K, and Jk agglutinins of potential significance (wanted positives). However, this measure avoids unwanted positive tests due to cold agglutinins. STUDY DESIGN AND METHODS: Using data from prior publications, actual risk calculations (ARCs) were made to predict the risk of eliminating the 37 degrees C reading, pretransfusion direct antiglobulin test (DAT), and routine indirect antiglobulin crossmatch (IAT-XM). ARCs used the equation: wanted positives missed x 0.34 (or 0.80) x 5 x percent antigen-positive, where 0.34 = percent of patients transfused (ARCs for 37 degrees C reading and DAT); 0.80 = percent of crossmatched patients transfused (ARCs for IAT-XM); 5 = average number of units transfused. Following elimination of the 37 degrees C reading, the impact of this change on patient care was monitored. Antibody detection and identification data and transfusion reaction reports for 6 months after the change were reviewed. Recently transfused patients with new antibodies were evaluated for immune hemolysis by review of clinical and laboratory data. The findings were compared with those from the same dates of the preceding year. RESULTS: The risk of transfusing incompatible blood by eliminating the DAT, IAT-XM, and 37 degrees C reading is approximately 1:13,000, 1:2,000, and 1:2,400 units transfused, respectively. The cumulative risk from eliminating all three tests is approximately. 1 :1,000 units. With respect to the 37 degrees C reading, there were no differences between the pre-change and post-change study periods in the incidence of reported transfusion reactions or cases of immune hemolysis associated with newly formed antibodies. However, unwanted positive tests decreased from 162 to 61 following elimination of the 37 degrees C reading. This represents a decrease of 20 percent in the number of samples requiring antibody identification annually. CONCLUSIONS: Eliminating the 37 degrees C reading from pretransfusion antibody screening tests imposes less risk than omitting the routine IAT-XM, and it avoids the time and costs of evaluating unwanted positive tests, thus reducing expenditures and delays in patient care.

Factor XIIIa-positive dermal dendritic cells and HLA-DR expression in radial versus vertical growth-phase melanomas.

Fifty nevomelanocytic lesions, including 10 typical compound nevi and 20 radial and 20 vertical growth-phase melanomas, were evaluated for factor XIIIa and HLA-DR (LN3) expression within dermal dendritic cells (DDCs) or dermal dendrocytes to determine if DDCs proliferate and/or participate as possible antigen-presenting cells in the local tissue response to benign and malignant nevomelanocytic lesions. There was no statistical difference in factor XIIIa staining of DDCs between nevi and radial or vertical growth-phase melanomas, suggesting that DDCs do not significantly proliferate in nevomelanocytic lesions. However, studies to determine proliferation rate, apoptosis, and influences of local mediators on cell growth and/or recruitment were not done. HLA-DR staining by DDCs was significantly increased (p<0.001) in both melanoma groups when compared to compound nevi, but did not significantly differ between radial and vertical growth-phase melanomas. The intensity of HLA-DR expression appeared to correlate with the presence or absence of lymphocytic inflammation; HLA-DR intensity was judged greater in melanomas characterized by a brisk and infiltrative lymphocytic host response. We propose that DDCs may participate in the dermal immune response to invasive melanomas, probably as antigen-presenting cells to skin-associated lymphocytes.