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Critical Commentary
1134 . W. Boeker
Critical Commentary to "Aggressive Thyroid Carcinoma with Predominant Cribriform Growth Pattern"
w.
Boeker
MOnster, Germany
In the present study, Akslen and coworkers describe a case of an advanced metastatic follicular carcinoma with tracheal and oesophageal infiltration as well as distant lung metastases. Histologically, the tumor showed a solid, trabecular growth pattern with follicular lumina (cribriform growth pattern), frequent mitoses, apoptoses, necrosis and vascular invasion. The patient died 15 months after the diagnosis, despite surgical, radio iodine and external radio therapy. The authors suggest that the cribriform variant of follicular carcinoma may be associated with poor prognosis, thus representing an independent feature of aggressive clinical behaviour. Against the background of this case, I would like to discuss two problems. The first problem concerns the tumor classification. In addition to the traditional classification into differentiated and undifferentiated follicular carcinomas, recent studies have disclosed the existence of a third group - that of poorly differentiated thyroid carcinomas 1,3,4 with an intermediate biological behaviour between differentiated and anaplastic carcinomas. The most important type of this poorly differentiated group is the insular carcinoma that grows in solid nests, diffuse sheets, trabeculae, festoons and papillae with a variable number of abortive follicles 2 • However, up to now, the morphological spectrum of this tumor group is not yet fully characterized. Sakamot0 5 includes in the insular carcinoma group only tumors with a solid pattern (non-glandular component). This would exclude tumors without follicular differentiation with a cribriform pattern (glandular component). According to Sakamoto's criteria, this case has to be classified as a differentiated follicular carcinoma. However, taking the criteria of Chan 2 , I personally would classify this case as a poorly differentiated carcinoma, insular type.
The second problem is whether this particular case is suitable to demonstrate that insular carcinomas of cribriform type have a less favorable prognosis. Regarding prognostic factors in follicular carcinomas, tumor size, wide invasion, vascular invasion and presence of distant metastases have been shown to be poor prognostic factors 2 • The present case does fulfil all of these worse factors indicating poor prognosis. So the suggestion whether cribriform growth pattern in the present case has any impact on the prognosis can neither be proven nor denied. To answer this question, further cases of this type of carcinoma have to be evaluated in order to determine the prognostic implications of cribriform growth pattern. References 1 Carcangiu ML, Zampi G, Rosai J (1984). Poorly differentiated ("insular") thyroid carcinoma, a reinterpretation of Langerhans' "wuchernde struma". Am J Surg Pathol8: 655 668 2 Chan JKC (1995) Tumors of the Thyroid and Parathyroid Glands. In: Fletcher CDM (Ed) Diagnostic Histopathology of Tumors, vol. 2, pp 705 - 764. Churchill Livingstone 3 Papotti M, Micca FB, Fovero A et al. (1993) Poorly differentiated thyroid carcinomas with primordial cell component, a group of aggressive lesions sharing insular, trabecular, and solid patterns. AmJ Surg Patholl7: 291- 301 4 Sakamoto A, Kasai N, Sugano H (1983) Poorly differentiated carcinoma of the thyroid, a clinicopathologic entity for a high risk group of papillary and follicular carcinomas. Cancer 52: 1849 -1855 5 Sakamoto A (1996) Poorly differentiated carcinoma of the thyroid: an aggressive tumor arising from thyroid follicular epithelium. In: Boeker W, Schmid KW (Eds): Current To~ics in Pathology. (in press) Schmid KW, Boeker W (1997) Schilddruse. In: Remmele (Ed), Band 4, 2. edition. (in press)
Prof. Dr. med. W. Boeker, Gerhard-Domagk-Institut f. Pathologie der WWU, Domagkstr. 17, D-48149 Munster
Critical Commentary to "Aggressive Thyroid Carcinoma with Predominant Cribriform Growth Pattern"
w.
Boeker
MOnster, Germany
In the present study, Akslen and coworkers describe a case of an advanced metastatic follicular carcinoma with tracheal and oesophageal infiltration as well as distant lung metastases. Histologically, the tumor showed a solid, trabecular growth pattern with follicular lumina (cribriform growth pattern), frequent mitoses, apoptoses, necrosis and vascular invasion. The patient died 15 months after the diagnosis, despite surgical, radio iodine and external radio therapy. The authors suggest that the cribriform variant of follicular carcinoma may be associated with poor prognosis, thus representing an independent feature of aggressive clinical behaviour. Against the background of this case, I would like to discuss two problems. The first problem concerns the tumor classification. In addition to the traditional classification into differentiated and undifferentiated follicular carcinomas, recent studies have disclosed the existence of a third group - that of poorly differentiated thyroid carcinomas 1,3,4 with an intermediate biological behaviour between differentiated and anaplastic carcinomas. The most important type of this poorly differentiated group is the insular carcinoma that grows in solid nests, diffuse sheets, trabeculae, festoons and papillae with a variable number of abortive follicles 2 • However, up to now, the morphological spectrum of this tumor group is not yet fully characterized. Sakamot0 5 includes in the insular carcinoma group only tumors with a solid pattern (non-glandular component). This would exclude tumors without follicular differentiation with a cribriform pattern (glandular component). According to Sakamoto's criteria, this case has to be classified as a differentiated follicular carcinoma. However, taking the criteria of Chan 2 , I personally would classify this case as a poorly differentiated carcinoma, insular type.
The second problem is whether this particular case is suitable to demonstrate that insular carcinomas of cribriform type have a less favorable prognosis. Regarding prognostic factors in follicular carcinomas, tumor size, wide invasion, vascular invasion and presence of distant metastases have been shown to be poor prognostic factors 2 • The present case does fulfil all of these worse factors indicating poor prognosis. So the suggestion whether cribriform growth pattern in the present case has any impact on the prognosis can neither be proven nor denied. To answer this question, further cases of this type of carcinoma have to be evaluated in order to determine the prognostic implications of cribriform growth pattern. References 1 Carcangiu ML, Zampi G, Rosai J (1984). Poorly differentiated ("insular") thyroid carcinoma, a reinterpretation of Langerhans' "wuchernde struma". Am J Surg Pathol8: 655 668 2 Chan JKC (1995) Tumors of the Thyroid and Parathyroid Glands. In: Fletcher CDM (Ed) Diagnostic Histopathology of Tumors, vol. 2, pp 705 - 764. Churchill Livingstone 3 Papotti M, Micca FB, Fovero A et al. (1993) Poorly differentiated thyroid carcinomas with primordial cell component, a group of aggressive lesions sharing insular, trabecular, and solid patterns. AmJ Surg Patholl7: 291- 301 4 Sakamoto A, Kasai N, Sugano H (1983) Poorly differentiated carcinoma of the thyroid, a clinicopathologic entity for a high risk group of papillary and follicular carcinomas. Cancer 52: 1849 -1855 5 Sakamoto A (1996) Poorly differentiated carcinoma of the thyroid: an aggressive tumor arising from thyroid follicular epithelium. In: Boeker W, Schmid KW (Eds): Current To~ics in Pathology. (in press) Schmid KW, Boeker W (1997) Schilddruse. In: Remmele (Ed), Band 4, 2. edition. (in press)
Prof. Dr. med. W. Boeker, Gerhard-Domagk-Institut f. Pathologie der WWU, Domagkstr. 17, D-48149 Munster