In the ATA guideline and other guides and publications on thyroid cancer, there are parameters recommended to be included in the pathology report [4]. It is very important that the information in the report is completely and clearly stated to evaluate the postoperative treatment need of the patients and to predict the prognosis. In our study, we showed that some of this information was missing in pathology reports even in the high-volume tertiary centers.
The tumor size is one of most crucial parameters that determines the patient's prognosis and treatment plan. For instance, tumors larger than 4 cm in size cannot be treated with lobectomy and may require prophylactic central lymph node dissection whereas microcarcinomas are accepted as low risk even if they are multifocal. Maximum dimension was reported in all our patients except two cases (0.14%). The tumors of those two were multifocal and the tumor size data was missing for an unknown reason. In a similar study by Kahn et al., the maximum dimension missing rate was 2.7%, and in the study by Isidro et al. it was reported as 26.4%[8, 9] .
The 2017 WHO classification, 15 subtypes of PTC were identified. The most common subtypes are; classic, follicular, diffuse sclerosing and tall cell variants[10]. Classic variant, follicular variant, tall cell variant and columnar variant were the most frequently reported variants in our study. As reported, some PTC variants are associated with a more aggressive course and unfavorable outcomes[11]. Therefore, ATA guideline recommends the PTC variant should be identified and reported (4). In our study, PTC variant was reported in 48.61% of the pathology results. Subtype classification rate was quite high in macrocarcinomas (88.7%) and significantly lower in microcarcinomas (11.2%). According to the 2017 WHO classification, papillary microcarcinoma was defined as a PTC variant[10]. Opposing that recommendation, the 2022 WHO classification suggested that papillary microcarcinoma should not be considered as a separate variant[12]. This new classification requires detailed subtyping of papillary microcarcinomas just as macrocarcinomas and recommends not designating them as a subtype of PTC. With this new WHO classification, we think that the reporting rate of microcarcinoma variants in our pathology results will increase in the future years.
Assessment of the surgical margin for PTC is a mandatory item that should be mentioned in the final histopathology report in accordance with the American College of Pathologists (CAP) guidelines and can be divided into three groups: a R0 resection (microscopically negative margin), a R1 resection (grossly complete resection with microscopically positive margin), and a R2 resection (grossly positive margin or incomplete resection)[13]. Histologically, a positive margin is defined by the presence of tumor cells at the inked tissue border and/or the outside of the thyroid gland[3]. The reported frequency of microscopically positive margin is between 6.1% and 14.1% in the previous studies [13–16]. Several recent studies have shown that microscopically positive margin is not an independent predictor for recurrence, disease specific mortality and disease-free survival, especially after adjusting for tumor stage and extrathyroidal extension[13, 14]. In the light of that finding, current ATA guidelines included only incomplete R2 resection in risk stratification as a feature of high-risk lesions[4]. Information about surgical margin was absent in 249 (17.69%) patients of our cohort which was significantly higher than previously reported as 7.1%[17]. In the other studies, the rate of underreporting of surgical margins was between 15.2% and 42.6% which was compatible with our results[9].
Extrathyroidal extension (ETE) is detected in 23.5% of all PTCs. Recent evidence suggests that the prognostic significance of minimal ETE is limited[18]. However, gross ETE is associated with a high risk of recurrence and considered as high-risk category. In our cases, the rate of ETE was reported as 17.6%. This item was missing in 9.1% of the pathology reports. Thyroid capsule invasion was missing in 46.5% of our reports. The thyroid gland does not have a complete capsule. At the periphery of the gland, follicles can be mistaken as adipose tissue that may lead to the lack of information regarding capsule invasion in some reports[19]. In 154 (62%) of 248 patients with ETE, it was not specified whether the ETE was minimal or extensive. Although it was not clearly stated in the pathology report, we think that ETE was minimal in most of those specific patients. In the study of Kahn et al. ETE was the least reported item. ETE was not reported in 49.1% of the patients in this study[9]. In addition, Isidro et al. reported this rate as 41.2% [8]
The College of American Pathologists guideline has divided lymphovascular invasion (LVI) into lymphatic invasion and vascular invasion (20).This situation has some disadvantages. This separation has spread into clinical management guidelines and created substantial confusion. The NCCN guidelines [21], for example, have used a term “degree of lymphatic invasion” whereas the ATA guidelines [4] have used term “vascular invasion”. In addition, it is difficult to distinguish between vascular invasion and lymphatic invasion by immunohistochemistry studies alone [22]. To avoid this confusion, the International Collaboration on Cancer Reporting (ICCR) suggested using the term LVI [23]. Although LVI alone does not determine the management of DTC, it is associated with the risk of lymph node metastasis [24–26]. LVI was missing in the report of 1020 (72.5%) patients. We think that the reason why LVI were missing in most patients in our study was due to its limited importance in the management of DTC.
Lymph node metastasis is a common finding especially in the course of PTC. It is a component of AJCC TNM staging. Presence of lymph node metastasis (N1) is divided into pN1a (central compartment or upper mediastinal lymph nodes) and pN1b (lateral compartment or retropharyngeal lymph nodes)(27). In addition, according to the ATA guideline, the risk category varies according to the number of lymph node metastases, the largest diameter and the presence of extra nodal extension (4). Therefore, it is important to report this item in pathology results. Lymph node metastases were detected in 153 of our patients. Metastatic lymph node size, number of lymph nodes examined, number of involved lymph nodes, and size of the metastatic focus were missing in the report at a rate of 39.8%, 7.8%, 2.6%, and 42.1%, respectively. The compartment of the metastasis was reported in all patients. It was not reported whether lymph node dissection was performed or not in 39.2% of those patients. This may be due to insufficient information of the pathologist by the surgical team. In the study of Isidro et al., the number and location of the affected lymph nodes were fully reported (8).
The major limitation of our study was absence of follicular thyroid carcinomas and poorly differentiated thyroid carcinomas. We had pathology reports of 2114 patients, but we could enroll 1407 of those whose histopathology reports were examined in our center. The data of patients with FTC and poorly differentiated cancers were primarily reported by other centers and they were excluded from the study.