event of any problems, he may find his affairs handled by nonprofessionals and may even have to resort to legal action against CUSO before things are settled. The CUSO experience is a potentially rewarding one but should be undertaken with a realization that a large measure of "self-sacrifice" is unquestionably involved. L.H. ROSSMAN, MD 999 Merivale Rd. Ottawa, Ont.
Solitary thyroid metastasis To the editor: I question the acceptability of the case report "Solitary thyroid metastasis from clear-cell renal carcinoma" by Madore and Lan (Can Med AssocJ 112: 719, 1975) as a bona fide example of renal-cell adenocarcinoma with late metastatic development in the thyroid gland. The authors have failed to present any evidence to distinguish between a metastatic clear-cell carcinoma and a primary clear-cell carcinoma of the thyroid. This well documented variant of . is reviewed by thyroid Chesky, Hellwig and Barbosa,3 who also contribute six cases from their clinic. They point out the difficulty in differentiating this entity from metastatic renal-cell adenocarcinoma. Kniseley and Andrews2 suggest that histochemical techniques may be helpful in making this distinction. This is affirmed by Meissner and Warren,1 who state that the cytoplasm of thyroid clear cells does not stain with periodic acid-Schiff (PAS) reaction or with Oil Red 0 as renal clear cells usually do. At present the literature contains too few cases to allow the formulation of a sound proposal as to the histogenesis and biologic behaviour of the clearcell carcinoma of the thyroid. The possibility that this tumour arises from parathyroid cell rests or pluripotential cells of thyroid origin3 or from transformed follicular cells induced by hormonal influence2 must be recognized as speculation only. The important fact remains that, morphologically, the clear-cell carcinoma of the thyroid represents a problem of diagnosis for the histopathologist. It must be distinguished from metastatic renal-cell adenocarcinoma as well as from other metastatic tumours that have a clear-cell pattern. R.H. PAiTERSON, MD Department of pathology Queen's University Kingston, Ont.
References 1. MEISSNER WA, WARREN S: Tumours of the thyroid gland, in Atlas of tumour pathology, second series, fascicle 4, Washington, DC, Armed Forces Institute of Pathology, 1969
2. KNISELEY RM, ANDREWS GA: Transformation of thyroidal carcinoma to clear-cell type. Am I Clin Pathol 26: 1427, 1956 3. CHESKY yE, HELLWIG CA, BARBOSA E: Clear cell tumours of the thyroid. Surgery 42: 282,
1957 4. SMITHERS D (ed): Tumours of the Thyroid Gland (vol VI). Edinburgh and London, Livingatone, 1970 5. WOOLNER LB, BEAHRS OH, BLACK BM, et al: Classification and prognosis of thyroid carci-
noma. A study of 885 cases observed in a thirty-year period. Am I Surg 102: 354, 1961
To the editor: We would like to thank Dr. Patterson for pointing out that primary clear-cell carcinoma of the thyroid should have been mentioned as a possibility in the case presented. The diagnosis was made by the pathology department of this hospital. The PAS reaction of the tumour was positive and this favoured a diagnosis of metastatic renal-cell carcinoma, as Dr. Patterson points out. One of the criteria in the diagnosis of primary clear-cell carcinoma of the thyroid is the absence of a primary in the kidney. Otherwise, one would have to suggest the possibility of two separate clear-cell carcinomas in the same patient, which we suppose could occur but must be extremely rare. However, Dr. Patterson is quite right in pointing out that not all clear-cell carcinomas in the thyroid are metastatic, an important practical point for the surgeon and the pathologist to remember. P. MADORE, MD
St. Mary's Hospital Montr6al, Quo.
was the high rate of severe congenital abnormalities in those taking meprobamate or chiordiazepoxide during the first 6 weeks of pregnancy. In those taking meprobamate in early pregnancy, the rate of severe abnormalities per 100 live births was 12.1%. This is more than 4½ times the 2.6% rate for the "no drug" group and 2½ times the rate for the "other drugs" group. In those taking chiordiazepoxide in early pregnancy the rate was 11.4%, more than four times the rate for the "no drug" group. Fetal death rates were considerably higher when the mothers had taken either meprobamate or chlordiazepoxide (Table I). Table I-Crude fetal death rates per 1000 single pregnancies Group Meprobamate Chlordiazepoxide Other drugs No drug
Gestation (wk)
Solitary thyroid metastasis To the editor: I question the acceptability of the case report "Solitary thyroid metastasis from clear-cell renal carcinoma" by Madore and Lan (Can Med AssocJ 112: 719, 1975) as a bona fide example of renal-cell adenocarcinoma with late metastatic development in the thyroid gland. The authors have failed to present any evidence to distinguish between a metastatic clear-cell carcinoma and a primary clear-cell carcinoma of the thyroid. This well documented variant of . is reviewed by thyroid Chesky, Hellwig and Barbosa,3 who also contribute six cases from their clinic. They point out the difficulty in differentiating this entity from metastatic renal-cell adenocarcinoma. Kniseley and Andrews2 suggest that histochemical techniques may be helpful in making this distinction. This is affirmed by Meissner and Warren,1 who state that the cytoplasm of thyroid clear cells does not stain with periodic acid-Schiff (PAS) reaction or with Oil Red 0 as renal clear cells usually do. At present the literature contains too few cases to allow the formulation of a sound proposal as to the histogenesis and biologic behaviour of the clearcell carcinoma of the thyroid. The possibility that this tumour arises from parathyroid cell rests or pluripotential cells of thyroid origin3 or from transformed follicular cells induced by hormonal influence2 must be recognized as speculation only. The important fact remains that, morphologically, the clear-cell carcinoma of the thyroid represents a problem of diagnosis for the histopathologist. It must be distinguished from metastatic renal-cell adenocarcinoma as well as from other metastatic tumours that have a clear-cell pattern. R.H. PAiTERSON, MD Department of pathology Queen's University Kingston, Ont.
References 1. MEISSNER WA, WARREN S: Tumours of the thyroid gland, in Atlas of tumour pathology, second series, fascicle 4, Washington, DC, Armed Forces Institute of Pathology, 1969
2. KNISELEY RM, ANDREWS GA: Transformation of thyroidal carcinoma to clear-cell type. Am I Clin Pathol 26: 1427, 1956 3. CHESKY yE, HELLWIG CA, BARBOSA E: Clear cell tumours of the thyroid. Surgery 42: 282,
1957 4. SMITHERS D (ed): Tumours of the Thyroid Gland (vol VI). Edinburgh and London, Livingatone, 1970 5. WOOLNER LB, BEAHRS OH, BLACK BM, et al: Classification and prognosis of thyroid carci-
noma. A study of 885 cases observed in a thirty-year period. Am I Surg 102: 354, 1961
To the editor: We would like to thank Dr. Patterson for pointing out that primary clear-cell carcinoma of the thyroid should have been mentioned as a possibility in the case presented. The diagnosis was made by the pathology department of this hospital. The PAS reaction of the tumour was positive and this favoured a diagnosis of metastatic renal-cell carcinoma, as Dr. Patterson points out. One of the criteria in the diagnosis of primary clear-cell carcinoma of the thyroid is the absence of a primary in the kidney. Otherwise, one would have to suggest the possibility of two separate clear-cell carcinomas in the same patient, which we suppose could occur but must be extremely rare. However, Dr. Patterson is quite right in pointing out that not all clear-cell carcinomas in the thyroid are metastatic, an important practical point for the surgeon and the pathologist to remember. P. MADORE, MD
St. Mary's Hospital Montr6al, Quo.
was the high rate of severe congenital abnormalities in those taking meprobamate or chiordiazepoxide during the first 6 weeks of pregnancy. In those taking meprobamate in early pregnancy, the rate of severe abnormalities per 100 live births was 12.1%. This is more than 4½ times the 2.6% rate for the "no drug" group and 2½ times the rate for the "other drugs" group. In those taking chiordiazepoxide in early pregnancy the rate was 11.4%, more than four times the rate for the "no drug" group. Fetal death rates were considerably higher when the mothers had taken either meprobamate or chlordiazepoxide (Table I). Table I-Crude fetal death rates per 1000 single pregnancies Group Meprobamate Chlordiazepoxide Other drugs No drug
Gestation (wk)
