Two cases of renal cell carcinoma, both of which underwent extensive spontaneous regression, are reported. The first occurred in a 56 year old man, forming a well circumscribed renal cortical nodule which contained only very occasional foci of viable renal cell carcinoma with areas of hyalinisation and calcification, and with metaplastic ossification. The second lesion was removed from an 82 year old man, comprising a cystic cavity containing necrotic debris with only occasional viable foci of classical renal cell carcinoma. Spontaneous regression of renal cell carcinoma is a rare but recognised entity. These two cases emphasise the important diVerential diagnoses: metastatic secondary carcinomas, xanthogranulomatous pyelonephritis, and infective granulomatous conditions of the kidney. The importance of adequate tissue sampling of all renal nodules cannot be overemphasised in the processing for examination of lesions within the kidney. (J Clin Pathol 1998;51:334-336)

This paper describes the immunohistology and molecular genetics of 18 cases of T-cell-rich B-cell lymphoma (TCRBL). In all cases, the large B cells stained strongly for CD20, with more variable expression of CD79a, and were negative for CD30 and CD15. The majority of T cells were predominantly positive for TIA-1 and negative for CD57; a large population of histiocytes was present in all cases. Epstein-Barr virus (EBV)-coded RNA (EBER) was found in B blasts from four cases and in one case was present among the background lymphoid cells. IgH PCR products were generated in 16/18 cases and revealed clonal, oligoclonal and polyclonal PCR products in 12, two and two cases, respectively. In addition, TCRG clonal gene rearrangements were identified in two cases. TCRB gene rearrangements were polyclonal. Sequence analysis of seven cases with clonal/oligoclonal IgH gene rearrangements revealed functional sequences with predominant V(H)3 gene usage associated with various D genes and J(H)4 or J(H)6 gene segments. Four cases displayed varying degrees of replacement and silent mutations (1.8-21%), with one case exhibiting intraclonal heterogeneity; the distribution of mutations was indicative of antigen selection in three cases. The remaining three cases, including two cases with functional oligoclonal IgH rearrangements, harboured unmutated V region genes. The EBV-positive cases were associated with clonal, oligoclonal and polyclonal PCR products and with mutated and germline clonal sequences. These data indicate that TCRBL may be a heterogeneous entity associated with clonal and oligoclonal B cells derived from both germinal centre and naïve B cells.

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