THYROIDVolume 6, Number 6, 1996Mary Ann Liebert, Inc.

Prognostic Impact of Thyroid Lymphocytic Infiltration inPatients With Medullary Thyroid Carcinoma

LUCIO SCOPSI,* PAOLA COLLINI,1 GIUSEPPE SAMPIETRO,1 PATRIZIA BORACCHI,2 andSILVANA PILOTTI1

ABSTRACT

A retrospective search for lymphocytic infiltration of the thyroid was performed on archival paraffin specimensfrom 95 cases of thyroid medullary carcinoma observed at a single institution during a 30-year period. A mildlymphocytic infiltration of the nonneoplastic thyroid tissue, mainly concentrated at the edge of the tumor mass,was observed in 33 cases, while in a further 24 cases a moderate to marked lymphocytic infiltration, resemblingthat seen in chronic lymphocytic thyroiditis, was homogeneously distributed all over the gland, with no appar¬ent relationship to the site of the primary tumor. Virtually no lymphocytic infiltration was detected inside of anyof the tumors. The presence of chronic lymphocytic thyroiditis seemed to be a characteristic of the host ratherthan a tumor-induced event. Statistical univariate analysis of relapse-free survival and overall survival showedthat lack of chronic lymphocytic thyroiditis marked those patients with an increased risk of disease recurrence

and death. However, the observed risk for survival was statistically nonsignificant, whereas that for disease re¬

currence was significant and remained in a multivariate model of statistical analysis.

INTRODUCTION

In the four decades that have elapsed since the originaldescription of Hazard and co-workers (1), the clinico¬

pathologic and genetic features of medullary thyroid car¬

cinoma (MTC) have been thoroughly evaluated (2).Though much attention has been paid to the characteris¬tics of the tumor itself (3), there has been less effort, mostlydealing with C-cell hyperplasia, to study the host organ.

This report assesses the status of lymphocytic infiltra¬tion (LI) of the primary tumor and nonneoplastic thyroidin a consecutive series of 95 MTCs and describes the re¬

sults in a prognostic perspective.

SUBJECTS, MATERIALS, AND METHODS

Selection of cases

Archival paraffin blocks of 117 consecutive MTCs ob¬served at the Istituto Nazionale Tumori of Milan, Italy,during a 30-year period (1964-1994), were retrieved.Hematoxylin and eosin sections from all of the blocks were

examined by three independent observers (LS, PC, and SP).

The histopathologic study was done without knowledge ofclinical characteristics and outcome of the patients. Thestatus of LI of the primary tumor and nonneoplastic thy¬roid was assessed separately in the right and left lobes andisthmus, and scored as: 0 = absent; 1 = a small number oflymphocytes scattered or in small clusters; 2 = numerous

lymphocytes forming follicles with germinal centers

(chronic lymphocytic thyroiditis, CLT); 3 = diffuse pres¬ence of lymphocytic infiltration with germinal centers andpresence of oncocytic metaplasia and fibrosis (CLT, au¬

toimmune type, also called Hashimoto's thyroiditis) (4).The presence of thyroid pathologies other than MTC andof intratumoral necrosis were also recorded. Doubtful cases

were reviewed and a consensus was obtained among thethree observers.

Adequate tissue material was available in 95 of the 117cases. Of these 95 cases, the whole thyroid gland was avail¬able in 56, for 34 of which right and left lobes and isth¬mus had been recorded separately. In the remaining 22cases, the isthmus was not sampled separately. In a further32 cases, specimens from one lobe only (generally that withthe tumor) were available. In the last 7 cases, the side ofthe normal thyroid tissue samples had not been recorded.

Endocrinology Unit, 'Division of Pathological Anatomy, Istituto Nazionale Tumori, Milan, Italy.2Istituto di Statistica Medica e Biometria, University of Milan, Milan, Italy.'Present address: Via Privata Giorgi, 30, 19038 Sarzana (SP), Italy.

613

614 SCOPSI ET AL.

Six of the 95 patients underwent an incomplete primarythyroid resection and received total thyroidectomy 6 to 26(median 14) years later.

Clinicopathologic characteristicsInformation relating to clinical features, investigations,

and management of the 95 cases selected was obtained.There were 46 male (48%) and 49 female (52%) patients.Age at surgery ranged from 16 to 75 years (mean and me¬

dian, 46 years), with no major differences between thesexes. Forty patients belonged to blood group 0, 38 to A,11 to B, and 3 to AB. Phenotypically, there were 90 ap¬parently sporadic cases and 5 familial cases (4 MEN 2A,and 1 MEN 2B). Staging was carried out based on the lastTNM recommendations (5). The main clinicopathologiccharacteristics are summarized in Table 1. Circulating thy¬roid hormones and TSH levels were normal in the 49 (11CLT+ and 38 CLT~) and 21 patients (4 CLT+ and 17CLT^), respectively, in whom they were measured preop-eratively. All patients were followed up to November 1995or to death. The median length of follow-up was 64 months(min 4, max 377). One fourth of the patients had a fol¬low-up >138 months. At the last follow-up, 51 patients

were still alive (20 disease-free), whereas the remaining 44were dead, 38 of whom died of their disease.

Statistical analysesStatistical analyses were performed by means of the

Statistical Analysis System package (SAS Institute, Cary,NC). Two classes of LI were considered: CLT~ includingcases with mild (score 1) or no LI, and CLT+ includingcases with LI score 2 and 3. The independence between theCLT status and the clinicopathologic variables just men¬

tioned were assessed by Chi-square statistics or, if neces¬

sary, Fisher's exact tests.

Relapse-free survival was calculated as the time elapsedfrom the date of primary surgery to the date of the firstdisease progression or to the date of the last clinical ex¬

amination. Overall survival was calculated as the timeelapsed from the date of primary surgery to the date ofdeath (for all causes) or to the date of the last information.Survival patterns were estimated by means of theProduct-Limit method. Because the proportional hazardassumption was tenable, the Cox regression model was

adopted. In this model, each of the regression coefficientsis the logarithm of the hazard ratio and appears to be con-

Table 1. Main Clinicopathologic Characteristics

Variables Classes Frequencies (%)Tumor size (cm)

Tumor focality

Thyroid capsule

Amyloid status

C cell hyperplasia

T*

N*

M*

Surgical excision (MO* patients only)

Postoperative calcitoninemia

<11^1>4

unknownsingle nodulemultiple nodulesunknownintactinfiltratedsoft tissue invasionunknownabsentscarceabundantabsentpresentunknown

1234X0lalbX01X

completeincompleteuncertainunknownnormalpathologicalunknown

14 (24.7)62 (65.3)15 (15.8)4 (4.2)

46 (48.4)43 (45.3)

6 (6.3)37 (38.9)30 (31.6)18 (18.9)10 (10.5)21 (22.1)41 (43.2)33 (34.7)56 (58.9)22 (23.2)17 (17.9)14 (14.7)50 (52.6)

6 (6.3)21 (22.1)

4 (4.2)27 (28.4)40 (42.1)25 (26.3)

3 (3.2)82 (86.3)10 (10.5)

3 (3.2)55 (67.1)6 (7.3)

15 (18.3)6 (7.3)

14 (14.7)26 (27.4)55 (57.9)

»Seeref. 5.

THYROIDITIS IN MEDULLARY CARCINOMA 615

stant over time. For two groups of patients under the nullhypothesis of the same relapse-free (or overall) survival ex¬

perience, the hazard ratio is expected to be 1.00. This hy¬pothesis was tested by the Wald statistic. In the univariateanalysis, a regression model containing only the variableCLT was interpolated and the unadjusted hazard ratio was

estimated.In the multivariate analysis, the CLT variable was added

to the final model obtained in a previous study in which18 clinicopathologic variables had been studied (6) to eval¬uate their joint effects. From the multiple regression model,the adjusted hazard ratios were estimated. The additionalcontribution of the CLT variable to the prognosis attainedby the clinicopathologic variables identified in a previouswork as important prognostic factors was evaluated by thelikelihood ratio test.

RESULTS

Fifty-seven of the 95 cases (60%) displayed some degreeof LI of the nonneoplastic thyroid parenchyma. LI was

mostly (n = 33) mild (score 1) and detected mainly aroundthe tumor mass. However, moderate to markedLI—whether (score 3) or not (score 2) associated with fea¬tures of Hashimoto's thyroiditis—was recorded in 16 and8 cases, respectively. In all these cases, LI was homoge¬neously distributed all over the thyroid gland.

In 32 cases, the nonneoplastic thyroid tissue showed thepresence of one or more follicular adenomas (« = 11) or

alterations typical of adenomatous hyperplasia (n = 24).Mild LI was detected in 13 and CLT in 3 of these 32 cases.

In 2 of these 32 cases and in a further case, all 3 lackingCLT, a micropapillary carcinoma was found synchro¬nously with MTC.

LI was virtually absent inside of the tumors. However,in 13 cases, necrosis was focally present in central areas ofboth large tumors and smaller tumoral nests, and in six ofthese cases a mild (score 1) LI was seen next to the necroticfoci.

CLT status was strongly associated with sex and, to aminor extent, with age. In fact, —80% of the CLT+ pa¬tients were females ( 1 = 9.786, p = 0.002), and CLT was

absent in patients below 30 years of age (Fisher's exacttest: p = 0.01). No statistically significant association was

found with the other clinicopathologic characteristics.Univariate statistical analysis of relapse-free survival

showed that CLT patients had a risk of recurrence 2.4times (95% confidence intervals: 1.0-5.4; p = 0.03) higherthan CLT+'s (Fig. 1). Univariate statistical analysis of over¬

all survival showed that CLT~ patients had a risk of death1.3 times (95% confidence intervals: 0.6-2.7; p = 0.47)higher than CLT+'s. Multivariate analysis was performedby adding the CLT variable to the final model (referred toas reference model in Table 2) obtained in an earlier workon the same case series (6). Except for a slight weakeningof the "sex" variable, this addition did not overtly modifythe prognostic impact of the variables considered in thereference model, but it did increase the prognostic infor¬mation, because the adjunctive contribution of the CLTvariable was statistically significant (see likelihood ratiotest, Table 2).

0 12 24 36 48 60 72 84 96 108 120MONTHS

FIG. 1. Relapse-free survival curves by chronic lymphocyticthyroiditis. Present (—), absent (—).

DISCUSSION

The coexistence of CLT and thyroid neoplasms has beenthe subject of several reports. Among the tumor types de¬scribed there are lymphomas (7), papillary and follicularcarcinomas (8), and rare variants (9-11).

Our results show for the first time the rather frequentoccurrence of LI in thyroids of MTC patients. This was

unexpected, because in none of the pathologic studies on

MTC performed so far (3), including the seminal papersby Hazard et al. (1) and Williams et al. (12), has such a

feature been noticed. In fact, whereas a number of reportsmay be found dealing with the relationship between CLTand C cell hyperplasia/hypercalcitoninemia (13), only a fewisolated cases have been described of an MTC arising in a

background of Hashimoto's thyroiditis (14-17).The majority of thyroids harboring an MTC had some

degree of LI, which in over half the cases was focal andmild. This type of infiltrate (so-called peri-tumor thyroidi¬tis) is frequently found at the periphery of neoplasms andis also observed in autoptic series (focal "nonspecific" lym¬phocytic thyroiditis), in the absence of gross thyroid lesions(4). However, in the remaining 40% of our MTC cases

presenting LI (i.e., in the 25% of the whole series) the pat¬tern of LI corresponded to that observed in chronic lym¬phocytic thyroiditis.

In contrast to papillary thyroid carcinomas (18), the in¬flammatory process in MTC patients seemed not to rep¬resent an antigenic response to the presence of the tumor.

First, CLT was not significantly associated with tumor size.

616 SCOPSI ET AL.

Table 2. Multivariate Analysis for Relapse-Free Survival(all 2 have one degree of freedom)

Reference Model (95 patients) AHR 95% CI X2

Sexfemale vs. male 2.34

Thyroid capsuleintact vs. infiltrated 1.30intact vs. soft tissue invasion 3.84

Amyloidpresent vs. absent 2.95 1.49-5.81

Contribution of the chronic lymphocytic thyroiditis variable to the reference model (85 patients)

1.20-4.59

0.59-2.831.74-8.46

Sexfemale vs. male

Thyroid capsuleintact vs. infiltratedintact vs. soft tissue invasion

Amyloidpresent vs. absent

Chronic Lymphocytic Thyroiditispresent vs. absent

Likelihood ratio test:Chronic Lymphocytic Thryoiditis

1.99

1.814.46

4.41

2.67

X2 = 3.841

0.94-4.23

0.81-4.081.85-10.74

2.16-9.02

0.90-7.91

= 0.05

6.227

0.44011.219

9.769

3.246

2.10411.122

16.57

3.145

0.0126

0.50700.0008

0.0018

0.0716

0.1460.0009

0.0001

0.0762

Abbreviations: AHR, adjusted hazard ratio; CI, confidence interval.

Second, its distribution within the thyroid gland was ho¬mogeneous and unrelated to the side in which the MTCoriginated. Third, in six patients undergoing an incompleteprimary tumor resection, the thyroid residues removed 6to 26 (median 14) years later showed no CLT.

CLT occurrence in our patient series does not seem eitherto be related to concomitant diseases of the follicular ep¬ithelium, because it was infrequently (10.6%) found in cases

with follicular adenomas or adenomatous hyperplasia.Thus, CLT in MTC patients seems not to differ from that

described in the absence of a discrete thyroid pathology (4).In fact, CLT+ patients were almost exclusively females over

30 years of age and CLT is known to affect mainly the fe¬male sex, with a peak incidence between 30 and 60 yearsof age (19). This is an unequivocal observation, becauseMTC is known to have no sex prevalence (20).

This notwithstanding, MTC patients with CLT seemedto perform better than those without CLT. In fact, in uni¬variate analysis, lack of CLT defined patients with a sig¬nificantly higher risk of disease progression. We have quan¬tified this risk and found it 2.4 times higher than that ofCLT+ patients. Though the low number of observations inthe CLT+ class poses limitations to the strength of the sta¬tistical tests, lack of CLT seemed to add significant (nega¬tive) prognostic information on relapse-free survival. Onthe other hand, addition of CLT did not apparently mod¬ify the prognostic impact of clinicopathologic variables likethyroid capsule status and amyloid, already demonstratedto be strong predictors of disease relapse (6). In this con¬

text, the slight weakening of the importance of gender ismost likely due to the strong association between sex andCLT status.

The importance of CLT as an independent predictor ofdisease recurrence is also supported by the lack of associ¬ation between CLT and thyroid capsule status, the latterbeing most important in this context (6). Incidentally, this

may explain the seemingly poor effect of CLT status on

survival, which is also strongly influenced by thyroid cap¬sule status (6). In fact, of the 18 pT4 patients, the 3 withCLT died of their disease 4 to 45 months from the onset.

Even though a cellular immune response has been iden¬tified in MTC patients (21,22), virtually no LI was foundinside of MTCs, and the mild LI detected close to necroticfoci in some of the tumors would seem to be reactive tonecrosis itself. On the contrary, intratumoral LI is a well-known feature of papillary thyroid carcinoma, where it hasprognostic implications (23,24).

Thus, thyroid LI in MTC patients appears to be an eventunrelated to the tumor itself, as opposed to papillary thy¬roid carcinoma, where it has been suggested to representa specific response to the development of the tumor (18).The seemingly more favorable outcome of CLT+ MTC pa¬tients could be due to a peculiar immune status of the in¬dividual, of which CLT is a marker. The role of CLT isthus intriguing and potentially important for the progno¬sis of MTC patients. Because MTC may be quite aggres¬sive, identification of a subset of patients that could bene¬fit from a specific immunological treatment is an attractivegoal.

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Address requests for reprints to:Lucio Scopsi, M.D., D.M.Sc.

Istituto Nazionale TumoriVia G. Venetian, 120133 Milan, Italy