Cytogenetic and immunohistochemical study of 42 pigmented microcystic chromophobe renal cell carcinoma (PMChRCC).

Pigmented microcystic chromophobe renal cell carcinoma (PMChRCC) is a recently described morphologic variant of ChRCC. We have identified 42 cases in 40 patients in the last 24 years. We have investigated their clinical, morphologic, immunohistochemical, and cytogenetic features. Chromosomal abnormalities of chromosomes 7 and 17 were evaluated by automated dual-color silver-enhanced in situ hybridization on paraffin-embedded tissue. Chromosomal imbalance was defined on the basis of changes in both chromosomal index and signal distribution. The main age was 60.20 years, being 34 males and 6 women. The mean tumor diameter was 4.84 cm, with 39 intrarenal tumors. Grossly, the tumors were solid with a brown dark colored. Microscopically, tumors consisted of pale and eosinophilic cells arranged in microcysts or microalveolar in a cribriform pattern; there were microcalcifications and a dark brown pigment, mostly extracellular. One case showed sarcomatoid transformation. All tumors were positive for epithelial membrane antigen (EMA), Claudin 7, and E-cadherin. Monosomy of 7 and 17 chromosomes was present in 1/36 cases and 2/37 cases, respectively. Polysomy of chromosome 7 and 17 was found in 26/36 cases and in 4/37, respectively. With a median follow-up of 74.05 months, 37 patients were alive without disease and two were alive with disease progression. PMChRCCs expand the morphologic spectrum of the ChRCC with an unusual immunohistochemical profile. Cytogenetically, they showed monosomy to chromosome (CHR) 17 as other ChRCCs and polysomy of CHR 7 infrequent to ChRCCs. We present the probably largest series of PMCRCC, confirming their low aggressive behavior, with exceptional sarcomatoid transformation and distant metastases.

Malignant peripheral nerve sheath tumor of the thyroid: a clinicopathological and ultrastructural study of one case.

Thyroid malignant peripheral nerve sheath tumors (TMPNST) are very uncommon neoplasms that can be confused with anaplastic carcinoma, Riedel's thyroiditis, or other soft tissue tumors that may occur in the thyroid region. An example of TMPNST is presented in this report. The tumor occurred in a 56-yr-old woman. Fine needle aspiration did not provide adequate material. After thyroidectomy, the lesion posed important problems in differential diagnosis. Immunohistochemical, molecular, and electron microscopic features were taken into consideration to arrive at the correct diagnosis. Tumor cells were focally positive for keratins, a feature that has not been described in peripheral nerve sheath tumors of the thyroid, but that has been occasionally seen in tumors from other locations. After thyroidectomy, the patient received radiotherapy. She is well without evidence of recurrence 10 mo after surgery.

Predicting Metastatic Risk of Gastrointestinal Stromal Tumors: Role of Cell Proliferation and Cell Cycle Regulatory Proteins.

Gastrointestinal stromal tumors (GIST) are a heterogeneous group of neoplasms whose biologic behavior is difficult to predict. The aim of this study is to evaluate the prognostic value in GIST of some oncoproteins involved in regulation of cell proliferation. Tumor size, mitosis, necrosis, and p53, c-myc, and bcl-2 protein expression of 32 GIST were studied. Proliferative index was assessed with Ki67. The 32 cases were grouped into the following clinical categories: (1) clinically benign (BN) were defined as disease-free survival greater than 3 years (n=10); (2) clinically malignant (MN) in which local recurrence or metastasis occurred regardless of the follow-up time (n=15); and (3) clinically indeterminate (ID) owing to follow-up <3 years without metastasis or local recurrence (n=seven). Discriminant analysis was used to allocate any tumor to one of the two prognostic groups (BN or MN). In univariate analysis all six factors studied above proved to be of significant prognostic value. Using a multivariate stepwise discriminant analysis to take into account the interrelationship between factors, we found that c-myc expression was the most important prognostic factor, followed, in order of statistical weight, by size and Ki67. These were combined to define a discriminant score ([10.75 x c-myc]+[0.39 x size]+[0.078 x Ki67]-15.54=score), which was capable of correctly identifying tumors in our series whose known clinical behavior was BN or MN in 92% of the cases. The classification score was applied subsequently to the seven clinically ID cases: Three (42.9%) were predicted as BN, and four (57.1%) were predicted as MN. Both expression of oncoprotein c-myc and the proliferative index provide prognostic information in GIST, in addition to morphologically established prognostic factors such as size. These factors in a discriminant analysis proved to be useful for the clinical classification of GIST into BN or MN and to predict the clinical outcome of clinically ID tumors. Int J Surg Pathol 8(2):133-144, 2000