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he reported rate of thyroid carcinoma amongall malignancies is approximately 1%.1In SaudiArabia, thyroid cancer was the second most

common malignancy after breast cancer,2 while it wasreported as the third most common in in the UnitedArab Emirates3 and fourth most common cancer inFilipino women.4

Te reported age-standardized incidence ratio ofthyroid cancer per 100 000 population in differentparts of the world varies from 0.8 to 0.5 for males and

1.9 to 19.4 for females.5Te life-time risk of develop--ing thyroid cancer in the US is about 1:120 for femaleswhile the risk of dying from the disease is approxi--mately 1 in 1700.6

Te cause of thyroid carcinoma is not known, butthere are some predisposing factors. Head and neck ir--radiation in childhood is a known predisposing factor,mainly for the papillary type.7Tere is also experimentalevidence suggesting an association between prolongedhigh levels of thyroid stimulating hormone (SH) and

fr e aderen plgy, m mel cllege, mrrk, sn, n Jnn pgre mel cenre, Kr,pkn

crrenene: uz bkr, md deren plgy, m mel cllege 864/83 bkr he, a twn, mrrk,sn 0007, pkn t: +033-43445593 zye@y. aee r ln Jne 2009

hel onl se cel ter 2009: 2(2); 345-348

Uzma Bukhari,aSaleem Sadiq,bJawaid Memon,aFarooq Baiga

Thyroid carcinoma in Pakistan: a retrospective

review of 998 cases from an academic referral

center

BACKGROUND AND OBJECTIVES: t re e nee r eelg n yr rn n

pkn, we evle e reqeny n ye yr rn w ree ge n ex.

METHODS: in rereve y ne e Jnn pgre mel cenre n Kr, werevewe yr len rere ver er 5 yer, r Jly 2000 Jne 2005. plgy le were

e eerne e ye n reqene lgnn len e yr.

RESULTS: o 998 yr len revewe, 153 e were lgnn. pllry rn w e n--

e lgnn len w reqeny 90.2%, llwe y 4.5% r ellry rn, 2% r lllr

rn, 2% r nerene rn n 0.7% e r xe ellry n llry rn

n rly erene rn. fele were renn (82.4%) re w le (17.6%) r

ele--le r 4.7:1. te x ner e en were n e r ee le llwe y

e r n en ee.

CONCLUSION: te ne lgnn yr len w llry rn. tyr ner w re --

n n ele. pllry, ellry n lllr rn were n n en n e r n r ee

le, wle rly n nerene rn were gne r e even ee le.

thyroid follicular adenoma and carcinoma.8Moreover,iodine deficient areas are known to have a high frequen--cy of follicular carcinoma.9

Unfortunately, the incidence of thyroid carcinoma inPakistan is difficult to assess due to the lack of popu--lation-based statistics, but its relative frequency in ourcountry is on the increase.10Te increase in frequencyin our population could be due to awareness of this dis--ease and other factors including genetic, dietary and en--vironmental factors.11Information on the geographical

distribution of cancer has been of great value for gen--eration of epidemiologic hypothesis and formulation ofconcepts for the etiology of cancer. Such informationwould also be valuable for making global comparisons.In an effort to address this need, we attempted to deter--mine the frequency and types of different carcinomasreceived over a period of five years.

METHODS

Tis was a retrospective study carried out in the

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Department of Pathology, Basic Medical SciencesInstitute, Jinnah Postgraduate Medical Centre, Karachi,Pakistan. Tyroid lesions seen over a 5-year period fromJuly 2000 to June 2005 were reviewed and cases of ma--

lignant lesions were selected for detailed study. Specialstains like periodic acid-Schiff (PAS), trichrome andCongo red were performed whenever required. Teclinical history and relevant data such as age and sexwas obtained from the records.

RESULTS

Of 998 thyroid lesions reviewed, 153 cases were diag--nosed as malignant lesions. Of these, papillary carcino--ma was the commonest thyroid carcinoma with a totalof 138 (90.2%). Tere were 7 (4.5%) cases of medullarycarcinoma followed by 3 (2%) cases each of follicularand undifferentiated carcinoma, while 1 (0.7%) case

each of mixed medullary and papillary carcinoma andpoorly differentiated carcinoma were seen (able 1).Of 138 papillary carcinomas, 72 cases were follicularvariants followed by 61 cases of classic papillary carci--noma and 5 cases of micropapillary carcinoma. Of the 7cases of medullay carcinoma, 3 were the follicular vari--ant and there was one case each of papillary, small cell,paraganglioma like and oncocytic variant of medullarycarcinoma was seen.

Females were predominant with a total of 126

(82.4%) as compared to males with a total of 27(17.6%). Te female-to-male ratio was 4.7:1. Te meanage for females was 32.6 years and for males 33.3 years.Most cases of papillary carcinoma, medullary carcinomaand follicular carcinoma were in patients in the fourthdecade of life followed by the third and second decades(able 2). However, poorly and undifferentiated carci--nomas were seen between 40 to 70 years of age.

DISCUSSION

Tyroid carcinomas represent the most common formof endocrine gland malignancy.12Primary lymphomasof the thyroid are uncommon while other non-epithe--lial malignancies are exceptionally rare.6Variation in thefrequency of thyroid carcinomas has been observed invarious parts of the world. We found papillary carci--noma as the commonest malignant lesion (90.2%). In

the USA, Hay13and Meier et al14also reported a similarfrequency of papillary carcinoma (90%). Other studiesfrom Lahore,15Yemen16 and Iran17have also reportedpapillary carcinoma as the commonest malignant thy--roid tumour with a variable frequency of 57.9%, 93.8%and 69.9%, respectively. Te mean age of our patientswas 32 years, which is slightly earlier as compared toShah et al18who found a mean age of 36.8 years.

Our study showed a predominancy of females(82.4%) in all carcinomas as compared with males(17.6%) with a female-to-male ratio of 4.7:1. Studies byseveral authors2,15,17also show a female predominancy

in thyroid cancers with a varying female-to-male ratioof 2.4:1, 4:1 and 3:1. Tis observation suggests that aspecific susceptibility gene with sex hormone receptorelements may be involved in the pathogenesis of thyroidcarcinoma. Tere is also expression of estrogen recep--tors on neoplastic thyroid epithelium. Most of our pa--tients were in the third and fourth decades of life, whichis similar to data reported by Ahmed et al.15

Te frequency of follicular carcinoma in our serieswas 2% (3 cases). However, a comparatively high fre--quency was reported by Abu-Eshy et al,19 Hundahl etal20and Abdullah21as 4.2%, 10% and 21.5%, respective--ly. For the diagnosis of follicular carcinoma strict criteria

need to be followed for capsular and vascular invasion.Tere is an interobserver variation between patholo--gists, which might be the reason for our small number offollicular carcinoma as compared to other studies.

Te current study showed a frequency of medullarycarcinoma of 4.5%, which is in agreement with a localstudy22and a study from Saudi Arabia,19the where re--ported prevalences of medullary carcinoma were 4.21%and 4.2%, respectively.

Mixed medullary and follicular cell carcinoma is a

Table 1. Distribution of 153 malignant lesions.

TypeNo. ofcases

Percentage

Papillary carcinoma 138 90.2

Follicular 72 -

Classic 61 -

Micropapillary 5 -

Medullary carcinoma 7 4.5

Follicular 3 -

Paraganglioma-like 1 -

Oncocytic cell 1 -

Papillary 1 -

Small cell 1 -

Follicular carcinoma 3 2

Undifferentiated carcinoma 3 2

Mixed medullary and papillarycarcinoma

1 0.7

Poorly differentiatedcarcinoma

1 0.7

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rare tumur and most have been described in single casereports. We found a single case of mixed medullary andpapillary carcinoma in a 25-year-old female. Our patientwas young compared to a case reported by Al-Mashat23of a 40-year-old female with this malignant tumor.

Poorly differentiated carcinoma remains a contro--versial entity, and it is therefore difficult to evaluatewhether the different prevalence rates among differ--ent geographic regions reflect true etiological differ--ences or mere variations in diagnostic criteria.24 Wereported a single case of poorly differentiated (insular)carcinoma (0.7%). Tis is not in accordance with a

study from northern Pakistan where two (9.5%) casesof insular carcinoma were reported in a total of 21 ma--lignant lesions.11Tis high frequency could be due toa relatively smaller number of total cases examined.Te current study showed 3 (2%) patients with un--differentiated carcinoma, which is in accordance withthe findings of Hussain et al22who reported 3 (3.2%)

Table 2. Age distribution of patients with 153 malignant lesions.

Type

Age groupsMeanage10-20

years

21-30

years

31-40

years

41-50

years

51-60

years

61-70

years

Papillary carcinoma 26 43 48 16 5 - 32.0

Medullary carcinoma 1 2 4 - - - 35.3

Follicular carcinoma - - 2 1 - - 45.8

Undifferentiated carcinoma - - - 1 1 1 58.3

Mixed medullary and papillarycarcinoma

- 1 - - - - 25.0

Poorly differentiated carcinoma - - - 1 - - 50.0

Total 27 46 54 19 6 1 32.4

Minimum age: male-14 years, female-15 years; maximum age: male-60 yearrs, female-70 years

patients with this carcinoma in a total of 95 cases.All our patients were females and were diagnosed inthe fifth, sixth and seventh decades of life, with meanage of 58.3 years. Studies by other workers2,17,20havealso reported a female predominance and an older agegroup for this carcinoma.

Te geographic variation in the prevalence rate ofthyroid cancer could be attributed to the iodine contentin food. It has been reported that after the introductionof iodine prophylaxis in various parts of the world, anincrease in the relative frequency of papillary carcinomaover follicular carcinoma has been observed.25Any sta--

tistical data about the disease draws attention towardsthe many important aspects like control, prevention andalso for further research. Since this is a laboratory-basedstudy, it has its own limitations. In this regard, a popu--lation-based study and estimation of iodine content inwater and food along with study of dietary habits in thecommunity is suggested.

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the difference in prevalence, survival and mortal--ity. Cancer 1998; 83:1757-1764.5. Tai P, Mould RF, Aye P, Gristchenko VG,Obodovsky IA. Descriptive epidemiology of thyroidcarcinoma. Current Oncology 2003; 10:54-65.6. DeLellis RA, Williams ED. Thyroid & ParathyroidTumours. In: WHO Classification of Tumours, Pa--

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