Letter to the Editor on “Should All Cases of High-Grade Serous Ovarian, Tubal, and Primary Peritoneal Carcinomas Be Reclassified as Tubo-Ovarian Serous Carcinoma?”

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In our opinion, the fact that one tumor type (HGSC) accounts for more than two thirds of the cases does not justify classifying ovarian carcinomas into only 2 types, lumping together the other four (low-grade endometrioid, clear cell, mucinous, and low-grade serous carcinomas) as “type 1 carcinomas”. In fact, the latter tumors are clinically, morphologically, and molecularly distinct diseases that individually bear resemblance neither to HGSCs nor to each other. Thus, classifying ovarian carcinomas into just 2 types (“types 1 and 2”) is artificial and limits progress in understanding the biology or improving the management of the less common types of ovarian carcinomas. When preparing this, we were reminded of the words of the eminent Scandinavian investigators of earlier times Drs. Lars Santesson and Hans Ludwig Kottmeier who began an essay on the classification of ovarian tumors as follows: “Ovarian cancer is not an entity but a group of diseases. Studies of the results of treatment must be based on homogeneous groups of tumours and not on mixtures of histologically and biologically different tumour types”.³

Just a few of the many differences between the entities in the grouping “type 1” carcinoma are the following: endometrioid and clear cell tumors have a very significant association with endometriosis, not seen, except rarely, with mucinous carcinomas and LGSCs. Additionally, endometrioid and clear cell carcinomas often have an origin in adenofibromas, also rarely seen with the other 2 tumor types. Mucinous tumors in an uncertain but definitely notable percentage of cases are likely of teratomatous origin, which is completely lacking for the other 3 tumor types....

 We think that terms such as tubo-ovarian, müllerian, or pelvic serous carcinoma should not be recommended because they create confusion for patients, physicians, and medical investigators. In view of the rarity of HGSCs associated with tubal tumor masses, it is unlikely that all HGSCs originate in the fallopian tube. In contrast, ovarian involvement is the rule in almost all cases. The term HGSC of ovary should be kept until the different origins of ovarian tumors are better understood.¹⁵

 REFERENCES

1. Moss EL, Evans T, Pearmain P, et al. Should all cases of high-grade serous ovarian, tubal, and primary peritoneal carcinomas be reclassified as tubo-ovarian serous carcinoma? Int J Gynecol Cancer. 2015; 25: 1201–1207.

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