Germline BAP1 mutations predispose also to multiple basal cell carcinomas.

The BRCA1-associated protein 1 (BAP1) gene encodes a nuclear deubiquitin enzyme which acts as a tumour suppressor. Loss of function germline mutations of BAP1 have been associated with an enhanced risk of uveal and cutaneous melanomas, mesothelioma, clear cell renal cancer and atypical cutaneous melanocytic proliferations. In two independent BAP1 families, we noticed an unusual frequency of basal cell carcinomas (BCCs). Indeed, 19 BCCs were diagnosed in four patients, either of superficial (13/19) or nodular (6/19) subtype; they were all located in chronic sun-exposed areas (limbs, head or neck). Immunohistochemistry (IHC) identified in the 19 tumours, complete or partial loss of BAP1 protein nuclear expression, restricted to the BCC nests. A control study was conducted in 22 sporadic BCCs in 22 subjects under 65 without known associated BAP1 tumours: no loss of BAP1 expression was found. Overall, our observations suggest that BCCs are part of the BAP1 cancer syndrome, perhaps in relation with chronic sun exposure and melanocortin 1 receptor (MC1R) variants. In conclusion, cutaneous follow-up of BAP1 carriers should not only aim to detect melanocytic neoplasms but also BCCs.

Malignant lymphoplasmacytic lymphoma with prominent splenomegaly (primary lymphoma of the spleen).

Eleven patients (age range 51-65 years) presenting with primary splenic lymphoma of lymphoplasmacytic type are described, together with detailed histological, immunohistochemical, and ultrastructural findings. The subclassification of this type of lymphoma is considered, and the prognosis discussed.

Bone marrow lambda-type light chain crystalline structures associated with multiple myeloma.

A 58-year-old man showed bone marrow crystalline structures associated with a lambda light chain producing multiple myeloma. Analysis and processing of electron images clearly displayed the periodic structure of the crystals. Immunochemistry suggested that they contained the whole or a fragmented constant portion of immunoglobulin.

[Immunohistochemical study of plasmocytes and T-lymphocyte subpopulations in Hashimoto's thyroiditis]. / Etude immunohistochimique des plasmocytes et des sous-populations T lymphocytaires dans la thyroïdite de Hashimoto.

In Hashimoto's thyroiditis, there is a diffuse interfollicular infiltration of lymphocytes and plasmocytes and lymphoid collections with germinal centers. Eleven cases of Hashimoto's disease were studied with immunocytochemical methods for characterization of intracytoplasmic immunoglobulins (IgA, IgG, IgM, Kappa and lambda light chains). Most of the cells are plasmocytes stained positively for intracytoplasmic IgG; IgA positive cells were less frequent and IgM positive cells are rare. Kappa positive plasma cells are more numerous than lambda positive cells in the germinal centers and the interfollicular infiltration. By an indirect immunofluorescence technique in frozen tissue, we have studied with four monoclonal antibodies (OKT3, OKT4, OKT8, B1) the T cells subsets populations in two cases.

Failure to distinguish ultrastructurally between T4+ (helper) and T8+ (suppressor/cytotoxic) T-cell subsets.

Human peripheral T-cell subpopulations revealed by monoclonal antibodies by means of a rosetting method were isolated by micromanipulation and submitted to electron microscopic analysis. The T3+ subset (total T cells) displayed a high degree of heterogeneity, including multiple transitional forms, from cells with a high nuclear to cytoplasmic ratio and rare organelles to cells with a low nuclear to cytoplasmic ratio and a complex system of cytoplasmic organelles. T4+ (inducer/helper) and T8+ (suppressor/cytotoxic) cell subpopulations were shown to have no evident distinguishing characteristics. They both displayed the same morphological variation mentioned for T3+ lymphocytes. On morphometric analysis, these two cell subsets were very similar, with only slight differences for cell surface roughness, volume of mitochondria, extent of nuclear indentation, and surface area of the rough endoplasmic reticulum. The significance of these minor morphological differences is discussed.