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Primary effusion lymphoma (PEL) is defined as a HHV-8-associated large B-cell lymphoma, which favors HIV-infected young adults, typically presenting as a serous (pleural, pericardial, or peritoneal) effusion with no identifiable tumor mass. Uncommon instances of lymphoid proliferations with the same morphology, immunophenotype, and molecular features as PEL, but occurring as a solid tumor mass without serous cavities involvement, have been termed extracavitary (or solid) variant of PEL. We hereby report the exceptional case of a HIV-associated extracavitary PEL primarily localized to the skin and exhibiting a panniculitis-like presentation. Primary cutaneous presentation of extracavitary PEL is exceedingly uncommon, with only 6 cases previously described in the literature. In light of its atypical immunophenotype, the differential diagnosis in case of skin involvement by extracavitary PEL is challenging: demonstration of HHV-8 infection in neoplastic cells is of pivotal importance. Our case is further atypical in that the lymphoid proliferation underwent complete and protracted regression solely by establishment of highly active antiretroviral therapy.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a neoplasm derived from precursors of plasmacytoid dendritic cells. Cutaneous involvement represents often the first manifestation of the disease. We studied 45 skin biopsies from 33 patients (M:F=7.25:1; median age: 71 y; age range: 30 to 89) with BPDCN to delineate histopathologic and immunophenotypic features of this disease. Patients presented with generalized (n=18), localized (n=6), or solitary (n=9) macules, plaques, and/or tumors. Staging investigations at presentation were negative in 20 patients. Unusual histologic features included a perivascular/periadnexal pattern (6 biopsies from 4 patients) and the presence of pleomorphism of neoplastic cells with blastoid cells admixed with elongated, twisted, or hyperchromatic cells (observed in 24 specimens). Negativity of 1 among the 4 markers CD4, CD56, CD123, and TCL-1 was seen in 11 biopsies, and of 2 markers in 4 biopsies. Staining for CD68 revealed positivity of the majority of cells in 1 and of scattered cells in 24/37 stained cases. Terminal deoxynucleotidyl transferase was observed in 22/37 stained cases. Staining for Bcl-6, MUM-1 and FOX-P1 revealed positivity of a variable proportion of neoplastic cells in 16/30, 19/29, and 21/23 cases, respectively. Our study shows that cutaneous lesions of BPDCN display a greater variability of morphologic and phenotypic features than recognized earlier. Discrete perivascular infiltrates, pleomorphic morphology of neoplastic cells, and unusual phenotypic profiles may be the source of diagnostic pitfalls. These atypical variants should be recognized to make an early diagnosis and to manage properly patients with this aggressive hematological disorder.

Immunohistochemical evaluation is, at present, the most reliable method to evaluate estrogen receptors (ERs) in breast cancer samples. Various quantitative 'scoring' systems have been developed to evaluate both the percentage of ER-positive nuclei and the staining intensity. However, such methods show a high interobserver variability. Densitometric evaluation of ERs provides objective results; however, it is scarcely reproducible because results are expressed in arbitrary units. Reproducibly to quantitate, as fmol/mg protein, the cell content of ERs detected by immunohistochemistry in frozen sections of breast cancer, we set up a densitometric method by using the MCF-7 cell cultures as standard. MCF-7 cell cultures were stimulated with insulin and insulin-like growth factor (IGF-1) to express variable concentrations of ERs. To reveal ERs with the same antibody clone, the immunoenzymatic study was carried out by using the ER-EIA method, whereas immunohistochemical reactions were based on ER-immunocytochemical assay (ICA) method. A standard curve, obtained by plotting the ER fmol/mg protein (by the enzymatic assay in MCF-7 cells) versus the optical-density values (by analyzing the immunohistochemical stain on MCF-7 cytospins), was the reference of our method. This method was validated on four cases of human infiltrating breast carcinoma, and no statistically significant differences were observed between ER concentration measured with the EIA method and that obtained by immunohistochemistry.