Occult papillary carcinoma of the thyroid. A study of 408 autopsy cases

Abstract

On examination of the thyroid glands in 408 consecutive autopsy cases, 64 occult papillary carcinomas (OPC) were found in 46 cases (11.3%) whose age ranged from 16 to 82 years. Their incidence was 26 of 247 (10.5%) in male and 20/161 (12.4%) in female cases. No definite correlation was found between the incidence of carcinoma and sex or age. All 64 carcinomas were less than 7.7 mm in diameter. They exhibited nuclear characteristics of papillary carcinoma although their growth patterns were "follicular" in the tumors less than 1 mm, and "papillary" in 70% of the tumors more than 3 mm in diameter. The carcinomas were classified into three types according to the presence or absence of capsular formation and fibrosis: encapsulated tumors (ET), nonencapsulated sclerosing tumors (NEST), and nonsclerosing tumors (NST). The NEST (28 tumors) and NST (26 tumors) were found in persons of all ages, whereas ET (ten tumors) were found only in those of older than 53 years. The mean tumor diameters of the three types, 4.57 mm for ET, 2.10 mm for NEST, and 0.85 mm for NST, were significantly different. These findings suggested that papillary carcinomas arose as minute carcinomas showing follicular pattern at any age as NST and then changed to NEST and ET, and papillary pattern became prominent if the tumors continued to grow. Very minute carcinomas were detected in serial sections of two of 27 fibrosclerotic nodules. Occult papillary carcinomas were found at significantly high incidence in cases with adenomatous goiter.

High Prevalence of Carcinoma in Ultrasonography-guided Fine Needle Aspiration Cytology of Thyroid Nodules

“…The majority of PMCs are not palpable and so clinically unapparent. In the past, many PMCs were found on pathology specimens from thyroid gland removed for benign thyroid diseases, such as Graves' disease, multinodular goiter, and hyperthyroidism or on autopsy of patients who had died of nonthyroid-related diseases [22][23][24][25]. However, in recent years there has been a considerable increase in the preoperative diagnosis and so in the relative rate of PMC [26][27][28].…”

Thyroid papillary microcarcinoma: a descriptive and meta-analysis study

“…Some US nodule characteristics appear suspicious for malignancy. Microcalcifications within malignant nodules have been observed in many studies (76,(127)(128)(129)(130) and were present in 7.1-59% of patients with PTMC (76,(127)(128)(129)(130)(131). Irregular margins of the nodules have been observed in 21.5-77% of PTMC (11,127,130,133).…”

“…An elevated prevalence of thyroid microcarcinoma has consistently been observed in the Japanese population, 13.7-28.4% (37,(75)(76)(77)(78). This may be related to radiation exposure during the bombing of Hiroshima and Nagasaki, but is probably due to ethnicity since Japanese residing in Hawaii, not exposed to bomb radiation, have a similar prevalence of thyroid microcarcinoma, 24% (37,79).…”

“…This may be related to radiation exposure during the bombing of Hiroshima and Nagasaki, but is probably due to ethnicity since Japanese residing in Hawaii, not exposed to bomb radiation, have a similar prevalence of thyroid microcarcinoma, 24% (37,79). In 4620 autopsy cases, PTMC was observed in 9.9% when only a suspected lesion was examined and in 15.5% of 1262 autopsy cases when the entire gland was examined (13,29,37,59,75,76,(80)(81)(82)(83)(84)(85). Therefore, the prevalence of occult thyroid microcarcinoma increases with the extent of the examination of the thyroid, in particular with the thinness of the anatomical slices of the thyroid specimens (29).…”

“…Irregular margins of the nodules have been observed in 21.5-77% of PTMC (11,127,130,133). A taller-than wider dimension and antero-posterior diameter larger than the transverse diameter of nonpalpable thyroid nodules have also been suggested as a diagnostic feature for the presence of malignancy (76,101). An increase in the size of small thyroid nodules at US follow-up was not a reliable marker in the differential diagnosis between malignant and benign nodules (132).…”