Primary cutaneous γδ T-cell lymphomas (PCGD-TCLs) are considered a subgroup of aggressive cytotoxic T-cell lymphomas (CTCLs). We have taken advantage of a new, commercially available antibody that recognizes the T-cell receptor-γ (TCR-γ) subunit of the TCR in paraffin-embedded tissue. We have analyzed a series of 146 primary cutaneous T-cell lymphomas received for consultation or a second opinion in the CNIO Pathology Department. Cases were classified according to the World Health Organization 2008 classification as mycosis fungoides (MF; n=96), PCGD-TCLs (n=5), pagetoid reticulosis (n=6), CD30(+) primary cutaneous anaplastic large cell lymphomas (n=5), primary cutaneous CD8 aggressive epidermotropic CTCLs (n=3), primary cutaneous CTCL, not otherwise specified (n=4), and extranodal nasal-type NK/T-cell lymphomas primarily affecting the skin or subcutaneous tissue (n=11). Sixteen cases of the newly named lymphomatoid papulosis type D (LyP-D; n=16) were also included. In those cases positive for TCR-γ, a further panel of 13 antibodies was used for analysis, including TIA-1, granzyme B, and perforin. Clinical and follow-up data were recorded in all cases. Twelve cases (8.2%) were positive for TCR-γ, including 5 PCGD-TCLs, 2 MFs, and 5 LyP-Ds. All 5 PCGD-TCL patients and 1 MF patient died of the disease, whereas the other MF patient and all those with LyP-D were alive. All cases expressed cytotoxic markers, were frequently CD3(+)/CD8(+), and tended to lose CD5 and CD7 expressions. Eight of 12 and 5 of 11 cases were CD30(+) and CD56(+), respectively. Interestingly, 5/12 TCR-γ-positive cases also expressed TCR-BF1. All cases analyzed were negative for Epstein-Barr virus-encoded RNA. In conclusion, TCR-γ expression seems to be rare and is confined to cytotoxic primary cutaneous TCLs. Nevertheless, its expression is not exclusive to PCGD-TCLs, as TCR-γ protein can be found in other CTCLs. Moreover, its expression does not seem to be associated with bad prognosis by itself, as it can be found in cases with good and bad outcomes.

In conclusion, immunohistochemical detection of spirochetes in paraffin-embedded samples is of great value for proper diagnosis of these types of cases, initially suspected of being a dendritic ⁄ reticular cell tumour ⁄ sarcoma.Although T. pallidum has already been shown to trigger nodal inflammatory pseudotumour, 5 some cases may show frank sarcomatous changes, as demonstrated here. Pathologists may take this into account in order to avoid overdiagnosing these lesions.

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We report the unique association of primary cutaneous marginal zone B-cell lymphoma and Rosai-Dorfman disease (RDD)-type histiocytic infiltrates involving the same lesions. The patient was an 82-year-old woman with 3 long-standing, well-circumscribed firm erythematous to brownish plaques on her left arm, right scapular area, and lumbosacral area. Histopathologic examination disclosed a dermal and subcutaneous nodular lymphoplasmacytic infiltrate with evidence of germinal center colonization and light-chain restriction and sheets of S-100 CD68-positive histiocytes with ample pale cytoplasm and occasional emperipolesis of lymphocytes. The neoplastic plasma cells expressed immunoglobulin (Ig) G4. A review of 14 examples of cutaneous RDD showed a substantial number of IgG4-positive cells in only 3 of them, and a review of 8 primary cutaneous marginal zone B-cell lymphomas disclosed only 2 with significant IgG4 expression. The coexistence of lymphomas and RDD has been rarely reported in the literature but only seldom involving the same lymph node and-to the best of our knowledge-never in the skin.

Cutaneous lesions in the setting of myeloproliferative neoplasms and myelodysplastic syndromes are poorly understood. We report 6 patients with pruritic papular eruptions composed of mature T-lymphocytes with large clusters of CD123-positive cells. Double immunohistochemical studies demonstrated a lack of myeloid cell nuclear differentiation antigen in the CD123-positive cells, which expressed SPIB, confirming that they were mature plasmacytoid dendritic cells. Four patients were diagnosed with chronic myelomonocytic leukemia and 2 with myelodysplastic syndromes (AREB-I and myelodysplastic syndromes with 5q deletion, respectively). All patients had a long history of hematological alterations, mainly thrombocytopenia, preceding the cutaneous disorder. Nevertheless, the skin lesions developed in all cases coincidentally with either progression or full-establishment of their hematological disease. Most cutaneous lesions disappeared spontaneously or after corticosteroid treatment. Molecular studies performed in both bone marrow and cutaneous lesions in 2 patients demonstrated the same mutational profile, confirming the specific, neoplastic nature of these mature plasmacytoid dendritic cells-composed cutaneous lesions.